Apparatus, system, and method of controlling session, and recording medium

ABSTRACT

A control apparatus determines one of a plurality of relay devices as a representative relay device to manage a relay destination of content data in a session to be established. In response to receiving a request for starting relay of content data, from a communication terminal, the control apparatus transmits, with a request for starting relay of content data, relay device identification information for identifying the representative relay device to a relay device connected to the communication terminal, to cause the relay device to further transmit the request for starting relay of content data to the representative relay device identified with the relay device identification information of the representative relay device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is based on and claims priority pursuant to 35U.S.C. §119(a) to Japanese Patent Application No. 2014-238740, filed onNov. 26, 2014, in the Japan Patent Office, the entire disclosure ofwhich is hereby incorporated by reference herein.

BACKGROUND

Technical Field

The present invention relates to an apparatus, system, and method ofcontrolling a session, and a control program stored on a recordingmedium.

Description of the Related Art

Communication systems such as videoconference systems that performcommunication or a conference via a communication network such as theInternet or a dedicated line have become popular in recent years due toa demand for reducing costs and time involved in movement of conferenceparticipants. When communication is started between communicationterminals in such a communication system, content data such as imagedata and sound data is transmitted or received, to carry outcommunication between the participants.

With this wide-spread use, there is a need for scalability incommunication systems. For example, as disclosed in Japanese PatentApplication Publication No. 2013-243471A, a plurality of videoconferencemanagement systems may be provided to disperse a connection destinationfor the communication terminal. Japanese Patent Application RegistrationNo. 4378651B (corresponding to WO 2005/004481A1) discloses a method oftransmitting image data via a plurality of multipoint control units(MCUs) to carry out communication among a plurality of end points. Thisincreases a number of end points that can be connected to one MCU.

SUMMARY

Example embodiments of the present invention include a control apparatusthat obtains information regarding a plurality of relay devices forrelaying content data in a session to be established among a pluralityof communication terminals, and determines one of the plurality of relaydevices as a representative relay device to manage a relay destinationof content data in the session to be established. In response toreceiving a request for starting relay of content data, from a firstcommunication terminal of the plurality of communication terminalssubject for participation in the session, the control apparatustransmits, with a request for starting relay of content data, relaydevice identification information for identifying the representativerelay device to a first relay device connected to the firstcommunication terminal, to cause the first relay device to furthertransmit the request for starting relay of content data to therepresentative relay device identified with the relay deviceidentification information of the representative relay device.

Example embodiments of the present invention include at least a firstcontrol apparatus and a second control apparatus. The first controlapparatus obtains information regarding a plurality of relay devices forrelaying content data in a session to be established among a pluralityof communication terminals, and determines one of the plurality of relaydevices as a representative relay device to manage a relay destinationof content data in the session to be established. The second controlapparatus receives, from a first communication terminal of the pluralityof communication terminals subject for participation in the session, arequest for starting relay of content data. The second control apparatusfurther transmits, with a request for starting relay of content data,the relay device identification information of the representative relaydevice to a first relay device connected to the first communicationterminal, to cause the first relay device to further transmit therequest for starting relay of content data to the representative relaydevice identified with the relay device identification information ofthe representative relay device. For example, the relay deviceidentification information of the representative relay device istransmitted from the first control apparatus to the plurality ofcommunication terminals subject for participation in the session. Thefirst communication terminal may send the relay device identificationinformation of the representative relay device with the request forstarting relay of content data.

Example embodiments of the present invention include a method ofcontrolling a session, which may be performed by the control apparatus.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A more complete appreciation of the disclosure and many of the attendantadvantages and features thereof can be readily obtained and understoodfrom the following detailed description with reference to theaccompanying drawings, wherein:

FIG. 1 is a schematic diagram illustrating a communication systemaccording to an embodiment of the present invention;

FIG. 2 is a state transition diagram illustrating the state transitionof a communication terminal in the communication system of FIG. 1;

FIG. 3 is an illustration of an example of a candidate list;

FIG. 4 is a perspective view illustrating an external view of thecommunication terminal of the communication system of FIG. 1 accordingto the embodiment of the present invention;

FIG. 5 is a schematic block diagram illustrating a hardwareconfiguration of the communication terminal of FIG. 4 according to theembodiment of the present invention;

FIG. 6 is a schematic block diagram illustrating a hardwareconfiguration of a control apparatus in the communication system of FIG.1 according to the embodiment of the present invention;

FIG. 7 is an overall configuration diagram of the communication systemof FIG. 1 according to the embodiment of the present invention;

FIG. 8 is a functional block diagram of the communication terminal, arelay device, the control apparatus, and a shared management apparatusof the communication system of FIG. 1;

FIGS. 9A to 9G are illustrations of management tables managed by thecontrol apparatus and the shared management apparatus included in amanagement system of the communication system of FIG. 1;

FIG. 10 is a sequence diagram illustrating a login operation of thecommunication terminal, according to an embodiment of the presentinvention;

FIG. 11 is a sequence diagram illustrating operation of displaying acandidate list on the communication terminal, according to an embodimentof the present invention;

FIGS. 12A and 12B are a sequence diagram illustrating operation ofsynchronizing operating states among control apparatuses, according toan embodiment of the present invention;

FIGS. 13A and 13B are a sequence diagram illustrating operation oftransmitting information between the communication terminals, accordingto an embodiment of the present invention;

FIGS. 14A and 14B are a sequence diagram illustrating operation ofstarting relaying content data, according to an embodiment of thepresent invention;

FIGS. 15A and 15B are a sequence diagram illustrating operation ofprocessing a request for participating in a session, according to anembodiment of the present invention;

FIGS. 16A and 16B are a sequence diagram illustrating operation ofprocessing a request for ending the session, according to an embodimentof the present invention; and

FIG. 17 is a sequence diagram illustrating logout operation of thecommunication terminal, according to an embodiment of the presentinvention.

The accompanying drawings are intended to depict example embodiments ofthe present invention and should not be interpreted to limit the scopethereof. The accompanying drawings are not to be considered as drawn toscale unless explicitly noted.

DETAILED DESCRIPTION

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the presentinvention. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“includes” and/or “including”, when used in this specification, specifythe presence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

In describing example embodiments shown in the drawings, specificterminology is employed for the sake of clarity. However, the presentdisclosure is not intended to be limited to the specific terminology soselected and it is to be understood that each specific element includesall technical equivalents that operate in a similar manner.

In the following description, illustrative embodiments will be describedwith reference to acts and symbolic representations of operations (e.g.,in the form of flowcharts) that may be implemented as program modules orfunctional processes including routines, programs, objects, components,data structures, etc., that perform particular tasks or implementparticular abstract data types and may be implemented using existinghardware at existing network elements or control nodes. Such existinghardware may include one or more Central Processing Units (CPUs),digital signal processors (DSPs),application-specific-integrated-circuits, field programmable gate arrays(FPGAs) computers or the like. These terms in general may be referred toas processors.

Unless specifically stated otherwise, or as is apparent from thediscussion, terms such as “processing” or “computing” or “calculating”or “determining” or “displaying” or the like, refer to the action andprocesses of a computer system, or similar electronic computing device,that manipulates and transforms data represented as physical, electronicquantities within the computer system's registers and memories intoother data similarly represented as physical quantities within thecomputer system memories or registers or other such information storage,transmission or display devices.

Referring to the drawings, an embodiment of the present invention isdescribed.

<Overview of Communication System>

At first, the overview of a communication system 1 according to anembodiment of the present invention will be described using FIG. 1. FIG.1 is a schematic diagram illustrating a transmission or reception stateof various types of information in the communication system 1.Hereinafter, a communication terminal is simply represented as a“terminal”.

The communication system 1 according to the embodiment includes aplurality of terminals (10 aa, 10 bb, and 10 cc), a plurality of relaydevices (30 xx, 30 yy, and 30 zz), and a control system 5. The controlsystem 5 includes a plurality of control apparatuses (50 x, 50 y, and 50z), and a shared information management apparatus (shared managementapparatus) 60. Hereinafter, an arbitrary one or ones of the plurality ofterminals (10 aa, 10 bb, and 10 cc) is/are represented as a “terminal(s)10”. In addition, an arbitrary one or ones of the plurality of relaydevices (30 xx, 30 yy, and 30 zz) is/are represented as a “relaydevice(s) 30”. In addition, an arbitrary one or ones of the plurality ofcontrol apparatuses (50 x, 50 y, and 50 z) is/are represented as a“control apparatus(s) 50”.

The terminal 10 performs communication through transmission or receptionof content data. One or more relay devices 30 relay content data betweena plurality of terminals 10. In doing so, one or more sessions areestablished for transmitting one or more items of content data betweenthe plurality of terminals 10. Here, a session for transmitting one ormore items of content data is represented as a session sed.

In response to terminals 10 participating in the session sed, contentdata is exchanged between the terminals 10, to carry out communicationbetween a plurality of offices, communication between different rooms inthe same office, communication within the same room, outdoor-indoorcommunication, or outdoor-outdoor communication. In the case where theterminals 10 are used outside, wireless communication using a mobilephone communication network or the like may be performed.

In this embodiment, the communication system is a system forestablishing a session send via a communication management system(corresponding to a “management system”) and intercommunicatinginformation, feelings and the like between a plurality of communicationterminals (corresponding to “terminals”).

In the embodiment, the communication system, the management system, andthe terminal will be described while assuming a videoconference systemserving as an example of the communication system, a videoconferencemanagement system serving as the communication management system, and avideoconference terminal serving as an example of the communicationterminal. That is, the terminal and the management system according tothe embodiment of the present invention are applied not only to avideoconference system, but also to a communication system. For example,the communication system 1 may be a phone system, and the terminal 10may be an Internet Protocol (IP) phone, an Internet phone, or a personalcomputer (PC).

In the embodiment, the term “videoconference” and the term“teleconference” are interchangeably used.

Furthermore, the case in which communication is performed by terminalssuch as videoconference terminals will be described. However, theembodiment is not limited to this case, and the embodiment is applicableto any case where communication in a broader sense includingconversations can be performed. For example, the communication system 1is applied to the case where an application accesses a server located ina center by itself and transmits or obtains various types of data. Inthis case, the communication partner may be a server, instead of aterminal. In addition, the terminal includes a game machine, a carnavigation apparatus, and the like. The communication system 1 is alsoan information sharing system, and the terminal 10 may be a projector,an electronic ad (digital signage), or an interactive whiteboard.

In the communication system 1 according to the embodiment, one or moreitems of content data transmitted between terminals 10 include, forexample, four items of data, namely, high-resolution image data,intermediate-resolution image data, low-resolution image data, and sounddata. The image data may be a video image or a still image, or both ofthe video image and the still image. The low-resolution image dataserves as a base image and has horizontal 160 pixels by vertical 120pixels. The intermediate-resolution image data has horizontal 320 pixelsby vertical 240 pixels. The high-resolution image data has horizontal640 pixels by vertical 480 pixels. According to the embodiment, in thecase of transmitting content data via a narrowband path betweenterminals 10, low-quality image data that only includes low-resolutionimage data serving as a base image is relayed. In the case oftransmitting content via a relatively wide band, intermediate-qualityimage data including low-resolution image data serving as a base imageand intermediate-resolution image data is relayed. In addition, in thecase of transmitting content data via a very wide band, high-qualityimage data including low-resolution image data serving as a base image,intermediate-resolution image data, and high-resolution image data isrelayed. Since sound data is smaller than image data in data size, thesound data is relayed even in the case of a narrow band path.

In the communication system 1 illustrated in FIG. 1, the plurality ofrelay devices 30 configure a relay system 3. Although the embodimentwhere three relay devices 30 relay content data among three terminals 10is illustrated in FIG. 1, the present invention is not limited thereto.For example, two relay devices 30 may relay content data among threeterminals 10, or three relay devices 30 may relay content data betweentwo terminals 10 in the communication system 1.

The shared management apparatus 60 manages information to be shared andused by the control apparatus 50, which includes various types ofinformation regarding terminals 10 or a session sed between theterminals 10 that the control apparatus 50 manages. In this disclosure,such information to be shared is referred to as shared information.

A session for transmitting various types of information is establishedvia the control apparatus 50 between terminals 10. Hereinafter, thissession will be represented as a session sei. Various types ofinformation transmitted between terminals 10 include a communicationstart request, a communication start permission, and a communication endrequest. The control apparatus 50 can detect the state of each terminal10 based on various types of information transmitted from the terminal10.

FIG. 2 is a state transition diagram illustrating an example of thestate transition of a terminal 10. In the state transition diagram ofFIG. 2, state information indicating the state of the terminal 10, suchas “None”, is written in each frame. When the terminal 10 logs in to acontrol apparatus 50 and becomes online, the communication state of theterminal 10, which has been logged in, becomes a standby state beforecommunication starts (a state indicated by the state information“None”). Next, when the terminal 10 sends a request for startingcommunication with another terminal 10, the communication state of theterminal 10 that is a start request sender becomes a state requesting tostart communication with another terminal 10 (a state indicated by thestate information “Inviting”), and the communication state of the otherterminal 10 which is a counterpart terminal becomes a state beingrequested by another terminal 10 to start communication (a stateindicated by the state information “Invited”). Next, when thecounterpart terminal 10 outputs a ringtone, the communication state ofthe counterpart terminal 10 becomes a state outputting a ringtone (astate indicated by the state information “Ringing”), and thecommunication state of the terminal 10 which is the start request senderbecomes a state outputting a dial tone (a state indicated by the stateinformation “Calling”). Next, when the counterpart terminal 10 permitsthe start request, the start request sender terminal 10 and thecounterpart terminal 10 enter a state where the start request has beenpermitted (a state indicated by the state information “Accepted”). Next,when the terminal 10 sends a request to start relaying content data, thecommunication state of the terminal 10 becomes a communicating state (astate indicated by the state information “Busy”). Next, when theterminal 10 sends a request to end the communication, the communicationstate of the terminal 10, which is an end request sender, returns to astate indicated by the state information “None”. In contrast, in thecase where the terminal 10 sends a request to participate in anestablished session sed, the communication state of the terminal 10,which is a participation request sender, becomes a state indicated bythe state information “Accepted”. Note that the rules of theabove-described state transition are only exemplary, and other rules maybe adopted in the communication system 1.

The control apparatus 50 each stores in a memory 5000 informationindicating the state transition rules illustrated in the statetransition diagram of FIG. 2. Accordingly, for example, when a terminal10 sends a start request, if the communication state of this startrequest sender terminal 10 is “None”, the control apparatus 50 transmitsthe start request to a counterpart terminal 10; if the communicationstate of the start request sender terminal 10 is not “None”, the controlapparatus 50 rejects the start request, for example. In doing so, thecontrol apparatus 50 can accurately perform calling control between theterminals 10.

In addition, besides the above-described communication state of eachterminal 10 subject for management, the control apparatus 50 manages theoperating state (presence) of the terminal 10 in order to, for example,notify the user of the terminal 10. Possible types of the operatingstate of each terminal 10 include the state “online (communication OK)”where the terminal 10 is connected to the control apparatus 50 but isnot communicating with another terminal 10, the state “online(communicating)” where the terminal 10 is connected to the controlapparatus 50 and is communicating with another terminal 10, and thestate “offline” where the terminal 10 is not connected to the controlapparatus 50. The control apparatus 50 notifies the terminal 10connected thereto of the operating state of the terminal 10 that is acandidate counterpart terminal of the notified terminal 10. In responseto transmission of the operating state from the control apparatus 50 tothe terminal 10, a display control 17 (FIG. 8) updates, based on thetransmitted operating state, an icon indicating an operating statedisplayed in a candidate list (see FIG. 3).

<Hardware Configuration of Communication System>

Now, a hardware configuration of the communication system 1 isdescribed. FIG. 4 is a perspective view illustrating an external view ofthe communication terminal 10 of the communication system 1 of FIG. 1.As illustrated in FIG. 4, the communication terminal 10 includes acasing 1100, an arm 1200, and a camera housing 1300. The casing 1100 hasa front wall 1110 provided with an inlet face including a plurality ofinlet holes, and a back wall 1120 having an exhaust face 1121 on which aplurality of exhaust holes is formed. As a cooling fan included in thecasing 1100 is driven, air behind the communication terminal 10 can betaken in via the inlet face and exhausted to the rear of thecommunication terminal 10 via the exhaust face 1121. A right-side wall1130 of the casing 1100 has a sound pickup hole 1131 formed thereon, anda built-in microphone 114, described later, is capable of picking upsound such as sound, noise, or vibration.

An operation panel 1150 is formed toward the right-side wall 1130 of thecasing 1100. The operation panel 1150 has a plurality of operation keys(108 a to 108 e) described later, a power switch 109, and an alarm lamp119, which are formed thereon. The operation panel 1150 further has asound output face 1151 formed thereon, which is formed of a plurality ofsound output holes for allowing output sound from a built-in speaker 115to pass through. In addition, an accommodation portion 1160 serving as arecess for accommodating the arm 1200 and the camera housing 1300 isformed toward a left-side wall 1140 of the casing 1100. A plurality ofconnection ports (1132 a to 1132 c) for electrically connecting cablesto an external device connection interface (I/F) 118 is provided on theright-side wall 1130 of the casing 1100. In contrast, a connection portfor electrically connecting a cable 120 c for a display 120 to theexternal device connection I/F 118 is provided toward the left-side wall1140 of the casing 1100.

The following description uses the term “operation key(s) 108” forindicating an arbitrary one or ones of the operation keys (108 a to 108e), and the term “connection port(s) 1132” for indicating an arbitraryone or ones of the connection ports (1132 a to 1132 c).

The arm 1200 is attached to the casing 1100 via a torque hinge 1210 soas to be rotatable in the vertical direction within the range of a tiltangle θ1 of 135 degrees with respect to the casing 1100. FIG. 4illustrates a state in which the tilt angle θ1 is 90 degrees. The camerahousing 1300 has a built-in camera 112 provided thereon, which cancapture an image of a user, a document, a room, or the like. The camerahousing 1300 is formed with a torque hinge 1310. The camera housing 1300is attached to the arm 1200 via the torque hinge 1310 so as to berotatable in the vertical and horizontal directions within the range ofa pan angle θ2 of ±180 degrees and a tilt angle θ3 of ±45 degrees withrespect to the arm 1200, in which the state illustrated in FIG. 4 servesas 0 degrees.

Note that the external view illustrated in FIG. 4 is only exemplary andthe appearance is not restricted thereto. The communication terminal 10may be a general-purpose PC, smart phone, or tablet. The camera 112 andthe microphone 114 need not necessarily be built-in devices and may beexternal devices.

Since the relay device 30, the control apparatus 50, and the sharedmanagement apparatus 60 each have the same appearance as that of ageneral server computer, a description of the appearance thereof isomitted.

FIG. 5 is a schematic block diagram illustrating a hardwareconfiguration of the communication terminal 10. As illustrated in FIG.5, the communication terminal 10 of the embodiment includes a centralprocessing unit (CPU) 101 that controls entire operation of thecommunication terminal 10, a read only memory (ROM) 102 that stores aprogram for operating the CPU 101 such as an initial program loader(IPL), a random access memory (RAM) 103 that operates as a work area forthe CPU 101, a flash memory 104 that stores various types of data, suchas the terminal control program, image data, and sound data, a solidstate drive (SSD) 105 that controls reading/writing of various types ofdata from/to the flash memory 104 under control of the CPU 101, a mediumI/F 107 that controls reading/writing (storage) of data from/to arecording medium 106, the operation key 108 operated in the case of, forexample, selecting a counterpart terminal of the communication terminal10, the power switch 109 for turning on/off the power of thecommunication terminal 10, and a network interface (I/F) 111 fortransmitting data using the communication network 2.

In addition, the communication terminal 10 includes the built-in camera112, which captures an image of a subject and obtains image data undercontrol of the CPU 101, an imaging element I/F 113 that controls drivingof the camera 112, the built-in microphone 114, which receives a soundinput, the built-in speaker 115, which outputs sounds, a soundinput/output I/F 116 that processes inputting/outputting of a soundsignal between the microphone 114 and the speaker 115 under control ofthe CPU 101, a display I/F 117 that transmits image data to an externaldisplay 120 under control of the CPU 101, the external device connectionI/F 118 for connecting various external devices, and a bus line 110 suchas an address bus and a data bus for electrically connecting theabove-described elements as illustrated in FIG. 5.

The display 120 is a display formed of liquid crystal or organicelectroluminescence (EL) that displays an image of a subject, anoperation icon, or the like. In addition, the display 120 is connectedto the display I/F 117 by the cable 120 c. The cable 120 c may be ananalog red green blue (RGB) (video graphic array (VGA)) signal cable, acomponent video cable, a high-definition multimedia interface (HDMI)signal cable, or a digital video interactive (DVI) signal cable.

The camera 112 includes a lens and a solid-state imaging element thatconverts an image (video) of a subject to electronic data by convertinglight to electric charge. As the solid-state imaging element, forexample, a complementary metal-oxide-semiconductor (CMOS) or acharge-coupled device (CCD) is used.

The external device connection I/F 118 is capable of connecting anexternal device such as an external camera, an external microphone, oran external speaker by using a Universal Serial Bus (USB) cable or thelike. In the case where an external camera is connected, the externalcamera is driven in preference to the built-in camera 112 under controlof the CPU 101. Similarly, in the case where an external microphone isconnected or an external speaker is connected, the external microphoneor the external speaker is driven in preference to the built-inmicrophone 114 or the built-in speaker 115 under control of the CPU 101.

The recording medium 106 is removable from the communication terminal10. In addition, a non-volatile memory that reads or writes data undercontrol of the CPU 101 is not limited to the flash memory 104, and anelectrically erasable and programmable read-only memory (EEPROM) may beused instead.

FIG. 6 is a schematic block diagram illustrating a hardwareconfiguration of the control apparatus 50 according to the embodiment.The control apparatus 50 includes a CPU 501 that controls entireoperation of the control apparatus 50, a ROM 502 that stores a programfor operating the CPU 501, such as an IPL, a RAM 503 used as a work areafor the CPU 501, the HD 504, which stores various types of data, such asthe control program for the control apparatus 50, a hard disk drive(HDD) 505 that controls reading/writing of various types of data from/tothe HD 504 under control of the CPU 501, a medium drive 507 thatcontrols reading/writing (storage) of data from/to a recording medium506 such as a flash memory, a display 508 that displays various types ofinformation such as a cursor, a menu, a window, characters, or an image,a network I/F 509 for transmitting data using the communication network2, a keyboard 511 including a plurality of keys for entering characters,numerals, and various instructions, a mouse 512 that selects andexecutes various instructions, selects a processing target, and movesthe cursor, a compact disc read-only memory (CD-ROM) drive 514 thatcontrols reading/writing of various types of data from/to a CD-ROM 513serving as an example of a removable recording medium, and a bus line510 such as an address bus and a data bus for electrically connectingthe above-described elements, as illustrated in FIG. 6.

Since the relay device 30 has a hardware configuration that is the sameas or similar to that of the above-described control apparatus 50,descriptions thereof are omitted.

Note that the control program for the communication terminal 10, thecontrol program for the relay device 30, the control program for thecontrol apparatus 50, and the control program for the shared managementapparatus 60 may each be recorded in a file in a format installable orexecutable on a computer-readable recording medium for distribution.Examples of such recording medium include, but not limited to, compactdisc-recordable (CD-R) and digital versatile disc (DVD). In addition, amemory storing any one of the above-described control programs, such asa recording medium including a CD-ROM or a HDD, may be provided in theform of a program product to users within a certain country or outsidethat country.

The control apparatus 50 and the shared management apparatus 60 in theabove-described embodiment may be configured by a single computer or aplurality of computers to which divided portions (functions) arearbitrarily allocated. The shared management apparatus 60 may beimplemented by any one or ones of the plurality of control apparatuses50 on the communication system 1.

<Overall Configuration of Communication System>

Next, using FIG. 7, the overall configuration according to theembodiment will be described. FIG. 7 is an overall configuration diagramof the communication system 1 according to the embodiment of the presentinvention.

The terminals 10, the relay devices 30, the control apparatuses 50, andthe shared management apparatus 60 are connected via the communicationnetwork 2 so as to be able to communicate with another terminal, device,or apparatus. The communication network 2 may be a local area network(LAN), the Internet, a mobile phone network, or a dedicated line. Thoughnot particularly limited, for example, communication between the relaydevices 30, communication between the control apparatuses 50, orcommunication between one control apparatus 50 and the shared managementapparatus 60 may be carried out through the communication network 2 thatis a dedicated line. Accordingly, communication between the devices orapparatuses can be stabilized. In addition, communication via thecommunication network 2 may include wired communication or wirelesscommunication.

The relay devices (30 xx and 30 xy) and the control apparatus 50 x arelocated in an area X. For example, the area X is Japan, and the relaydevices (30 xx and 30 xy) and the control apparatus 50 x are located ina data center in Tokyo.

The relay devices (30 yy and 30 yz) and the control apparatus 50 y arelocated in an area Y. For example, the area Y is the United States, andthe relay devices (30 yy and 30 yz) and the control apparatus 50 y arelocated in a data center in New York.

The relay devices (30 zz and 30 zx) and the control apparatus 50 z arelocated in an area Z. For example, the area Z is Southeast Asia, and therelay devices (30 zz and 30 zx) and the control apparatus 50 z arelocated in a data center in Singapore.

The terminals (10 aa, 10 bb, and 10 cc) are each portable, and mayconnect to the communication network 2 from the respective areas (X, Y,and Z) or from other areas.

In the communication system 1, four or more terminals 10 may beprovided. The shared management apparatus 60 may be located in any ofthe areas (X, Y, and Z), or may be located in an area other than theseareas. The relay devices 30 and the control apparatus 50 may be locatedin areas other than the areas (X, Y, and Z).

<Functional Configuration of Embodiment>

Referring now to FIGS. 5, 6, and 8, a functional configuration of thecommunication system 1 of FIG. 1 is described according to theembodiment of the present invention. FIG. 8 is a schematic block diagramillustrating a functional configuration of the communication system 1 ofFIG. 1 according to the embodiment of the present invention.

<Functional Configuration of Terminal>

The terminal 10 includes a transmitter/receiver 11, an acceptor 12, acommunication control 13, a display control 17, and a data processor 19.These units are functions that are implemented by or that are caused tofunction by operating any of the elements illustrated in FIG. 5 incooperation with the instructions of the CPU 101 according to theterminal program expanded from the flash memory 104 to the RAM 103. Theterminal 10 further includes a memory 1000 configured by the RAM 103 andthe flash memory 104. The terminal 10 is inserted with a recordingmedium 1010, which is implemented by the recording medium 106. The dataprocessor 19 reads or writes various data from or to the recordingmedium 1010.

(Functional Configuration of Terminal)

Next, functional configuration of the terminal 10 is explained indetail. In the following description of functional configuration of theterminal 10, relationships of the elements in FIG. 5 with the functionalconfiguration of the terminal 10 in FIG. 5 will also be described.

The transmitter/receiver 11, which is implemented by a command from theCPU 101 and by the network I/F 111, transmits or receives various typesof data (or information) to/from another terminal, device, apparatus, orsystem via the communication network 2.

The acceptor 12, which is implemented by a command from the CPU 101,accepts various inputs such as operation of the operation keys 108 bythe user or pressing of the power switch 109 by the user. For example,when the user turns on the power switch 109, the acceptor 12 accepts thepower on operation and turns on the power.

The communication control 13, which is implemented by a command from theCPU 101 and by the camera 112 and the imaging element I/F 113, capturesan image of a subject and outputs image data obtained by capturing theimage. In another example, the communication control 13 is implementedby a command from the CPU 101 and by the sound input/output I/F 116.After the sound of the user is converted to a sound signal by themicrophone 114, the communication control 13 receives sound dataaccording to this sound signal. Furthermore, in another example, thecommunication control 13 is implemented by a command from the CPU 101and by the sound input/output I/F 116. The communication control 13outputs a sound signal according to sound data to the speaker 115, andthe speaker 115 outputs sound.

The display control 17, which is implemented by a command from the CPU101 and by the display I/F 117, controls to combine items of receivedimage data having different resolutions and transmit the combined imagedata to the display 120. The display control 17 can also transmit to thedisplay 120 information received from the control apparatus 50, anddisplay the information on the display 120.

The data processor 19, which is implemented by a command from the CPU101 and by the SSD 105, or by a command from the CPU 101, performsprocessing to store various types of data in the memory 1000 or therecording medium 1010 or to read various types of data stored in thememory 1000 or the recording medium 1010. The memory 1000 stores aterminal identification (ID) for identifying each terminal 10, apassword, and the like. Alternatively, at least one of the terminal IDand the password may be recorded on the recording medium 1010 and may beread out by the data processor 19. In this case, the recording medium1010 may be implemented by a subscriber identity module (SIM) card, orIntegrated Circuit (IC) card. For example, the user may insert therecording medium 1010 that may be purchased into the terminal 10, toreceive communication services from the administrator of the controlsystem 5.

Further, every time image data and sound data are received in performingcommunication with a counterpart terminal, the memory 1000 overwritesthe image data and sound data. The display 120 displays an image basedon image data before being overwritten, and the speaker 115 outputssound based on sound data before being overwritten.

Note that a terminal ID in the embodiment is an example ofidentification information that is used to uniquely identify a specificterminal 10, such that a language, a character(s), a symbol(s), orvarious marks are not limited to the above-described embodiment. Forexample, a combination of at least two of the above-mentioned language,character(s), symbol(s), and various marks may be used as a terminal ID.Instead of a terminal ID, a user ID for identifying the user at theterminal 10 may be used. In such a case, terminal identificationinformation includes not only the terminal ID, but also the user ID.

(Functional Configuration of Control Apparatus)

The control apparatus 50 includes a transmitter/receiver 51, anauthenticator 52, a manager 53, a searcher 54, a session control 58, anda data processor 59. These units are functions that are implemented byor that are caused to function by operating any of the elementsillustrated in FIG. 6 in cooperation with the instructions of the CPU501 according to a program for the control apparatus 50, which isexpanded from the HD 504 to the RAM 503. In addition, the controlapparatus 50 includes a memory 5000 configured by the HD 504.

The memory 5000 of the control apparatus 50 stores the area IDs of areas(X, Y, and Z) where the control apparatus 50 or other controlapparatuses 50 are located. For example, the memory 5000 stores the areaID “jp01” indicating Japan where the control apparatus 50 x is located,the area ID “us01” indicating the U.S. where the control apparatus 50 yis located, and the area ID “sg01” indicating Singapore where thecontrol apparatus 50 z is located.

In addition, the memory 5000 stores an authentication management DB 5001configured by an authentication management table, a terminal managementDB 5002 configured by a terminal management table, a candidate listmanagement DB 5003 configured by a candidate list management table, asession management DB 5004 configured by a session management table, arelay device management DB 5011 configured by a relay device managementtable, an operating state management DB 5012 configured by an operatingstate management table, and a connection management DB 5013 configuredby a connection management table.

(Authentication Management Table)

FIG. 9A is an illustration of an example data structure of theauthentication management table. In the authentication management table,a terminal ID for identifying a corresponding terminal 10, a password,and the service ID of a service usable by the terminal 10 are managed inassociation with one another. The description will be continued byassuming that the terminal IDs of the terminals (10 aa, 10 bb, and 10cc) are “01aa@xx.com, 01bb@xx.com, and 01cc@xx.com”, respectively. Since“@xx.com” included in the terminal IDs are common among the terminals10, “@xx.com” will be appropriately omitted. Further, while in thisexample, it is assumed that the service Ill corresponds to a name ofapplication that can be installed for use by the terminal 10, theservice Ill may be expressed in any other form such as a symbol uniquelyassigned to each application.

(Terminal Management Table)

FIG. 9B is an illustration of an example data structure of the terminalmanagement table. In the terminal management table, for the terminal IDof each terminal 10, a counterpart terminal name (such as a terminalname), state information indicating the communication state of theterminal 10, an IP address indicating the address of the terminal 10,the area ID of a control apparatus 50 serving as a connectiondestination of the terminal 10, and the relay device ID of a relaydevice 30 serving as a connection destination of the terminal 10 aremanaged in association with one another.

(Candidate List Management Table)

FIG. 9C is an illustration of an example data structure of the candidatelist management table. In the candidate list management table, for theterminal ID of a terminal 10 serving as a communication start requestsender, the terminal IDs of terminals 10 that are candidate counterpartterminals specifiable by the terminal 10 which is the start requestsender are associatively managed.

(Session Management Table)

FIG. 9D is an illustration of an example data structure of the sessionmanagement table. In the session management table, for a session ID foridentifying a corresponding session sed, the terminal IDs of terminals10 participating in the session sed are associatively managed. In theembodiment, in the case of transmitting content data in a session sedvia a plurality of relay devices 30 between terminals 10, one relaydevice 30 manages the whole relaying of content data, and this relaydevice 30 serves as the origin to provide the other relay device(s) 30with information indicating a relay destination of the content data, andthe like. Therefore, the session ID includes domain information (such as“001xx”) indicating a relay device (such as the relay device 30 xx)serving as the origin in the session sed. For this reason, the sessionID (such as “conf01”) is displayed with the relay device ID (such as“001xx”).

(Relay Device Management Table)

FIG. 9E is an illustration of an example data structure of the relaydevice management table. In the relay device management table, for therelay device ID of a relay device 30, the area ID of an area where therelay device 30 is located, and the uniform resource identifier (URI) ofthe relay device 30 are associatively managed.

(Operating State Management Table)

FIG. 9F is an illustration of an example data structure of the operatingstate management table. In the operating state management table, for theterminal ID of a terminal 10, the operating state (presence) of theterminal 10 is associatively managed.

(Connection Management Table)

FIG. 9G is an illustration of an example data structure of theconnection management table. In the connection management table, for theterminal ID of a terminal 10, a relay device connection ID generatedwhenever the terminal 10 connects to a relay device 30, and a relaydevice connection password used in authenticating the terminal 10 whenthe terminal 10 connects to the relay device 30 are associativelymanaged.

(Functional Configuration of Control Apparatus)

Next, functional configuration of the control apparatus 50 will bedescribed in detail. In the following description of functionalconfiguration of the control apparatus 50, relationships of the elementsin FIG. 6 with the functional configuration of the control apparatus 50will also be described.

The transmitter/receiver 51, which is implemented by a command from theCPU 501 and by the network I/F 509, transmits or receives various typesof data (or information) to/from each terminal, device, apparatus, orsystem via the communication network 2.

The authenticator 52, which is implemented by a command from the CPU501, authenticates a terminal 10 by searching the authenticationmanagement table (see FIG. 9A) using a terminal ID and a passwordreceived by the transmitter/receiver 51 as search keys and determiningwhether the same terminal ID and the same password are managed in theauthentication management table.

The manager 53, which is implemented by a command from the CPU 501,manages each of the above-described management tables by adding ordeleting various types of information to or from each management table.

The searcher 54, which is implemented by a command from the CPU 501,searches for a node that is a terminal 10 connected to another controlapparatus 50.

The session control 58, which is implemented by a command from the CPU501, controls a session sed for transmitting content data betweenterminals 10. The above-mentioned control includes control forestablishing a session sed, control for causing terminals 10 toparticipate in the established session sed, and control fordisconnecting the session sed.

The data processor 59, which is implemented by a command from the CPU501 and by the HDD 505, or by a command from the CPU 501, performsprocessing to store various types of data in the memory 5000 or to readvarious types of data stored in the memory 5000.

(Functional Configuration of Shared Management Apparatus)

The shared management apparatus 60 includes a transmitter/receiver 61and a data processor 69. These units are functions that are implementedby or that are caused to function by operating any of the elementsillustrated in FIG. 6 in cooperation with the instructions of the CPU501 according to the sharing control program expanded from the HD 504 tothe RAM 503. In addition, the shared management apparatus 60 includes amemory 6000 configured by the HD 504. The memory 6000 stores anauthentication management DB 6001 configured by an authenticationmanagement table, a terminal management DB 6002 configured by a terminalmanagement table, a candidate list management DB 6003 configured by acandidate list management table, and a session management DB 6004configured by a session management table. Note that the authenticationmanagement DB 6001, the terminal management DB 6002, the candidate listmanagement DB 6003, and the session management DB 6004 on the sharedmanagement apparatus 60 side, and the authentication management DB 5001,the terminal management DB 5002, the candidate list management DB 5003,and the session management DB 5004 on each control apparatus 50 side aresynchronized with each other, such that common information are managed.

(Functional Configuration of Shared Management Apparatus)

The transmitter/receiver 61, which is executed by a command from the CPU501 and by the network I/F 509, transmits or receives various types ofdata (or information) to/from another terminal, device, apparatus, orsystem via the communication network 2.

The data processor 69, which is executed by a command from the CPU 501and by the HDD 505, or by a command from the CPU 501, performsprocessing to store various types of data in the memory 6000 or to readvarious types of data stored in the memory 6000.

(Functional Configuration of Relay Device)

The relay device 30 includes a transmitter/receiver 31, an authenticator32, and a data processor 39. These units are functions that areimplemented by or that are caused to function by operating any of theelements illustrated in FIG. 6 in cooperation with the instructions ofthe CPU 501 according to the relay device program expanded from the HD504 to the RAM 503. In addition, the relay device 30 includes a memory3000 configured by the HD 504 illustrated in FIG. 4.

(Functional Configuration of Relay Device)

The transmitter/receiver 31, which is executed by a command from the CPU501 and by the network I/F 509, transmits or receives various types ofdata (or information) to/from another terminal, device, apparatus, orsystem via the communication network 2.

The authenticator 32, which is implemented by a command from the CPU501, authenticates a terminal 10 by determining whether a combination ofa terminal ID, a relay device connection ID, and a relay deviceconnection password received by the transmitter/receiver 31 is managedin the connection management table (see FIG. 9G) on the controlapparatus 50 side.

The data processor 39, which is executed by a command from the CPU 501and by the HDD 505, or by a command from the CPU 501, performsprocessing to store various types of data in the memory 3000 or to readvarious types of data stored in the memory 3000.

<Process or Operation of Embodiment>

Next, a process or an operation of the terminal 10, the relay device 30,the control apparatus 50, and the shared management apparatus 60included in the communication system 1 will be described in detail.

(Login Process)

First, using FIG. 10, an operation where a terminal 10 logs in to acontrol apparatus 50 and to a relay device 30 will be described. FIG. 10is a sequence diagram illustrating a login operation of the terminal 10.

According to the embodiment of the present invention, a terminal 10 canlog in to one arbitrary control apparatus 50 among the plurality ofcontrol apparatuses 50. The method of selecting a control apparatus 50serving as a login request destination of each terminal 10 is notparticularly limited. For example, the method of selecting a controlapparatus 50 on the basis of information input to a terminal 10, themethod of selecting a control apparatus 50 closest to a terminal 10 onthe basis of the physical position information on the terminal 10, orthe method of selecting a control apparatus 50 using GSLB may be used.

The terminal 10 transmits, by using the transmitter/receiver 11, a loginrequest and its IP address to a selected, arbitrary control apparatus 50(step S1). The login request includes the terminal ID and password ofthe terminal 10, which is the login request sender. In response totransmission of a login request from the terminal 10, the IP address ofthe terminal 10 is transmitted to the control apparatus 50 serving as alogin request destination. Accordingly, the transmitter/receiver 51 ofthe control apparatus 50 receives the login request including theterminal ID and password, and the IP address of the terminal 10.

Next, the authenticator 52 refers to the authentication management table(FIG. 9A) and authenticates the terminal 10, which is the login requestsender (step S2). Here, in the case where the same combination as thecombination of the terminal ID and password transmitted from the loginrequest sender is managed in the authentication management table, theauthenticator 52 successfully authenticates the terminal 10, which isthe login request sender. In contrast, in the case where the samecombination as the combination of the terminal ID and passwordtransmitted from the login request sender is not managed in theauthentication management table, the authenticator 52 failsauthentication of the terminal 10, which is the login request sender.Hereinafter, the case of successful authentication will be continuouslydescribed.

The data processor 59 searches the authentication management table byusing the terminal ID of the terminal 10, which is the login requestsender, as a search key, and reads out a corresponding service ID, whichis part of processing in step S2.

Next, the manager 53 assigns an area ID indicating an area where thecontrol apparatus 50 is located, to the terminal 10, which is the loginrequest sender (step S3). The area ID is stored in advance in the memory5000 of the control apparatus 50. For example, if the control apparatus50 which has accepted the login request is the control apparatus 50 xlocated in the area X (Japan), the manager 53 assigns “jp01” as the areaID to the terminal 10, which is the login request sender.

Next, on the basis of a request from the manager 53, the data processor59 stores the operating state “online” in association with the terminalID of the terminal 10, which is the login request sender, in theoperating state management table (see FIG. 9F) (step S4).

In addition, the manager 53 manages the communication state of theterminal 10, which is the login request sender, in accordance with therules of the state transition illustrated by the state transitiondiagram of FIG. 2 (step S5). That is, in response to the operating statebecoming “online” in step S4, the manager 53 determines the stateinformation indicating the new state of the terminal 10, which is thelogin request sender, as “None” (see FIG. 2).

In the case where the service ID read out in step S2 is“videoconference”, the session control 58 selects a relay device 30serving as a connection destination of the terminal 10, which is thelogin request sender (step S6). In this case, the session control 58selects a relay device 30 identified by a relay device ID managed in thesession management table in association with the area ID (such as“jp01”) of an area (such as the area X) where the control apparatus 50is located, that is, a relay device 30 located in the same area as thecontrol apparatus 50, as a relay device 30 serving as a connectiondestination of the terminal 10, which is the login request sender. Inthe case where a plurality of relay devices 30 are located in the samearea as the control apparatus 50, the method of selecting a relay device30 is not particularly limited. For example, the method may be one thatselects a relay device 30 by using round robin, or one that selects arelay device 30 on the basis of the load on each relay device 30. Aspart of processing in step S6, the data processor 59 searches the relaydevice management table (see FIG. 9E) by using the relay device ID ofthe selected relay device 30 as a search key, thereby reading out acorresponding URI.

The session control 58 of the control apparatus 50 also generates arelay device connection ID used by the terminal 10, which is the loginrequest sender, to connect to the relay device 30 selected in step S5(step S7). As part of processing in step S7, the data processor 59associates the generated relay device connection ID and a relay deviceconnection password in association with the terminal ID of the terminal10, which is the login request sender, in the connection managementtable (see FIG. 9G). Note that the relay device connection password maybe determined in advance for each relay device 30, or may be generatedwhenever a terminal 10 connects to a relay device 30.

The transmitter/receiver 51 of the control apparatus 50 transmits aterminal management table updating request to the shared managementapparatus 60 (step S8-1). The updating request includes the terminal IDand IP address of the terminal 10, which is the login request sender,the area ID assigned in step S3, the state information determined instep S5, and the relay device ID of the relay device 30 selected in stepS6. Upon receipt, by the transmitter/receiver 61 of the sharedmanagement apparatus 60, of the updating request, the data processor 69associatively stores the terminal ID, IP address, state information,area ID, and relay device ID, which are included in the updatingrequest, in the terminal management table (see FIG. 9B) on the sharedmanagement apparatus 60 side.

Thereafter, the transmitter/receiver 61 of the shared managementapparatus 60 transmits the updated details of the terminal managementtable including the terminal ID, state information, area ID, relaydevice ID, and so forth to each of the control apparatuses (50 x, 50 y,and 50 z) included in the communication system 1. Upon receipt, by thetransmitter/receiver 51 of each control apparatus (50 x, 50 y, and 50z), of the updated details, the data processor 59 of each controlapparatus 50 updates the terminal management table therein on the basisof the received updated details. Accordingly, the terminal managementtable on each control apparatus (50 x, 50 y, and 50 z) side issynchronized with the terminal management table on the shared managementapparatus 60 side (steps S8-2-1, S8-2- . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 transmits,to the terminal 10, which is the login request sender, theauthentication result indicating successful authentication, the URI ofthe relay device 30 read out in step S6, the relay device connection IDgenerated in step S7, and the relay device connection password (stepS9).

Upon receipt, by the transmitter/receiver 11 of the terminal 10, of theURI, relay device connection ID, and relay device connection passwordtransmitted from the control apparatus 50, the transmitter/receiver 11transmits a login request to the relay device 30 indicated by the URI(step S10). The login request includes the terminal ID of the terminal10, which is the login request sender, and the relay device connectionID and the relay device connection password, which are transmitted fromthe control apparatus 50.

In the relay device 30, which has received the login request, theauthenticator 32 authenticates the terminal 10, which is the loginrequest sender (step S11). In this case, the authenticator 32 sends, viathe transmitter/receiver 31, an inquiry to the control apparatus 50located in the same area as the relay device 30, as to whether the samecombination as the combination of the terminal ID, relay deviceconnection ID, and relay device connection password included in thelogin request is managed in the connection management table (see FIG.9G) on the control apparatus 50 side. On the control apparatus 50 side,which has received the inquiry, the manager 53 refers to the connectionmanagement table and transmits the inquiry result to the relay device 30via the transmitter/receiver 51. In the case where the same combinationas the combination of the terminal ID, relay device connection ID, andrelay device connection password included in the login request ismanaged in the connection management table on the control apparatus 50side, the authenticator 32 successfully authenticates the terminal 10,which is the login request sender. In contrast, in the case where thesame combination as the combination of the terminal ID, relay deviceconnection ID, and relay device connection password included in thelogin request is not managed in the connection management table on thecontrol apparatus 50 side, the authenticator 32 fails authentication ofthe terminal 10, which is the login request sender. Thetransmitter/receiver 31 of the relay device 30 transmits theauthentication result to the terminal 10, which is the login requestsender (step S12).

Hereinafter, the case of successful authentication will be continuouslydescribed.

(Candidate List Request)

Next, using FIG. 11, an operation until a candidate list indicatingcandidate counterpart terminals of the terminal 10 is displayed on theterminal 10 will be described. FIG. 11 is a sequence diagramillustrating an operation of displaying a candidate list on the terminal10. In response to reception of the authentication result by theterminal 10, the transmitter/receiver 11 transmits a candidate listrequest that includes the terminal ID of the terminal 10 and thatindicates a request for a candidate list to the control apparatus 50 viathe communication network 2 (step S21). Accordingly, thetransmitter/receiver 51 of the control apparatus 50 receives thecandidate list request.

Next, the data processor 59 searches the candidate list management table(see FIG. 9C) by using the terminal ID of the terminal 10, which is thecandidate list request sender, as a search key and extracts the terminalID of a terminal 10 serving as a candidate counterpart terminal that canbe specified as a counterpart terminal by the terminal 10, which is thecandidate list request sender (step S22). In addition, the dataprocessor 59 searches the terminal management table (see FIG. 9B) byusing the extracted terminal ID as a search key, and reads out acounterpart terminal name. The transmitter/receiver 51 of the controlapparatus 50 transmits the terminal ID and counterpart terminal name ofeach candidate counterpart terminal, read out by the data processor 59,to the terminal 10, which is the candidate list request sender (stepS23).

Upon receipt of candidate list information by the transmitter/receiver11 of the terminal 10, which is the candidate list request sender, thedisplay control 17 of the terminal 10 displays, on the display 120, acandidate list reflecting each specifiable candidate counterpartterminal name, on the basis of the terminal ID(s) and counterpartterminal name(s) included in the candidate list information (see FIG. 3)(step S24).

According to the embodiment of the present invention, in the case ofadding a candidate counterpart terminal to the candidate list ordeleting a candidate counterpart terminal from the candidate list, theterminal 10 transmits a candidate list management table updating requestincluding the terminal ID of a terminal 10 serving as a candidatecounterpart terminal to be added or deleted, and the terminal ID of theterminal 10, to the control apparatus 50 (step S25). In the controlapparatus 50 which has received the updating request, on the basis of arequest from the manager 53, the transmitter/receiver 51 transmits acandidate list management table updating request to the sharedmanagement apparatus 60 (step S26-1). This updating request includes theterminal ID of the terminal 10, which is the updating request sender,and the terminal ID of a terminal 10 that is a candidate counterpartterminal to be added or deleted. The data processor 69 of the sharedmanagement apparatus 60 adds, as the terminal ID of a candidatecounterpart terminal associated with the terminal ID of the terminal 10,which is the updating request sender, the terminal ID of a candidatecounterpart terminal to be added, which is included in the updatingrequest, in the candidate list management table. Alternatively, the dataprocessor 69 of the shared management apparatus 60 deletes, among theterminal ID(s) of a candidate counterpart terminal(s) associated withthe terminal ID of the terminal 10, which is the updating requestsender, the terminal ID of a candidate counterpart terminal to bedeleted, which is included in the updating request, from the candidatelist management table.

Thereafter, the transmitter/receiver 61 of the shared managementapparatus 60 transmits the updated details of the candidate listmanagement table to each control apparatus (50 x, 50 y, and 50 z)included in the communication system 1. Upon receipt of the updateddetails by the transmitter/receiver 51 of each control apparatus (50 x,50 y, and 50 z), the data processor 59 of each control apparatus 50updates the candidate list management table therein on the basis of thereceived updated details. Accordingly, the candidate list managementtable on each control apparatus (50 x, 50 y, and 50 z) side issynchronized with the candidate list management table on the sharedmanagement apparatus 60 side (steps S26-2-1, S26-2-2, . . . ).

(Operating State Management)

Next, using FIGS. 12A and 12B (FIG. 12), as an example of inter-nodecooperation, an operation of synchronizing, among the controlapparatuses (50 x, 50 y, and 50 z) included in the control system 5, theoperating state of each terminal 10 managed by the control apparatuses(50 x, 50 y, and 50 z) will be described. FIG. 12 is a sequence diagramillustrating an operation of synchronizing operating states among thecontrol apparatuses 50.

When a terminal 10 (terminal 10 aa in this case) logs in to a controlapparatus 50 (control apparatus 50 x in this case), the searcher 54 ofthe control apparatus 50 x searches for a node that is a terminal 10serving as a candidate counterpart terminal (terminals (10 bb and 10 cc)in this case) (step S41-1 and S41-2). This node search is an operationexecuted to detect to which control apparatus 50 a terminal 10 servingas a candidate counterpart terminal that is not connected to the localcontrol apparatus 50 is connected. Therefore, the node search isexecuted on, among terminals 10 serving as candidate counterpartterminals, a terminal 10 that is not connected to the local controlapparatus 50.

For simplicity, in this disclosure, from the viewpoint of a specificuser, the control apparatus 50 that the terminal 10 operated by thatuser connects may be referred to as a local control apparatus 50 forthat terminal 10. In this disclosure, however, the term “local” does notrestrict a physical or a network site where the control apparatus 50 islocated, but the term “local” is used to specify one control apparatus50 that connects to the terminal 10 operated by the user, rather thangenerally referring to an arbitrary control apparatus 50. Moreover,while the control apparatus 50 is illustrated as one apparatus, one ormore apparatus may together function as the control apparatus 50, suchthat a number of apparatuses or devices is not restricted to one as longas the control apparatus 50 operates as a server.

In the case of executing the node search, on the basis of a request fromthe searcher 54, the transmitter/receiver 51 of the control apparatus 50x transmits search information for the node search to the other controlapparatuses (50 y and 50 z) (steps S41-1 and S41-2). The searchinformation includes the terminal ID of the terminal 10 aa connected tothe local control apparatus 50 x, and the terminal IDs of terminals (10bb and 10 cc) serving as candidate counterpart terminals that are notconnected to the local control apparatus 50 x.

Upon receipt of the search information by the transmitter/receiver 51 ofeach of the control apparatuses (50 y and 50 z), each session control 58determines whether terminals (10 bb and 10 cc) identified by theterminal IDs included in the search information are connected to thelocal control apparatus (steps S42-1 and S42-2). A publicly known methodis used as the method of determining connection with each terminal 10,though the method is not particularly limited. For example, the methodmay be one that determines whether each terminal 10 is connected, on thebasis of whether a time exceeding a certain threshold has passed sincethe last reception of information that is periodically sent from theterminal 10 in the session sei. In the case where each session control58 determines that the terminals (10 bb and 10 cc) identified by theterminal IDs are not connected to the local control apparatus (NO insteps S42-1 and S42-2), these control apparatuses 50 y and 50 z do notrespond to the control apparatus 50 x that is the search informationsender, and ends the operation. Hereinafter, the case where each sessioncontrol 58 determines that one of the terminals (10 bb and 10 cc)identified by the terminal IDs is connected to the local controlapparatus (YES in steps S42-1 and S42-2) will be continuously described.

The data processor 59 of each of the control apparatuses (50 y and 50 z)reads out, from the operating state management table (see FIG. 9F), anoperating state corresponding to the terminal ID of a terminal (10 bb or10 cc) connected to the local control apparatus, among the terminals 10serving as candidate counterpart terminals included in the searchinformation (steps S43-1 and S43-2).

Next, the transmitter/receiver 51 of each of the control apparatuses (50y and 50 z) transmits, as a response to the search information, anotification including the terminal ID of a terminal (10 bb or 10 cc)connected to the local control apparatus, and the operating state readout in step S42-1 or S43-2, to the control apparatus 50 x (steps S44-1and S44-2). Upon receipt of each notification by thetransmitter/receiver 51 of the control apparatus 50 x, the searcher 54identifies a control apparatus 50 that is the notification sender as aconnection destination of a terminal (10 bb or 10 cc) identified by theterminal ID included in the notification. Next, the transmitter/receiver11 transmits each received notification to the terminal 10 aa, which haslogged in (steps S45-1 and S45-2). Upon receipt of the notifications bythe transmitter/receiver 11 of the terminal 10 aa, the display control17 updates icons indicating the operating states of the terminals (10 bband 10 cc) serving as candidate counterpart terminals in the candidatelist (see FIG. 3), on the basis of the terminal IDs and operating statesof the candidate counterpart terminals (10 bb and 10 cc) included in therespective notifications (steps S46-1 and S46-2).

In contrast, in the control apparatus 50 x, on the basis of a requestfrom the manager 53, the data processor 59 stores the operating statesincluded in the notifications transmitted from the control apparatuses(50 y and 50 z), in association with the terminal IDs of the terminals(10 bb and 10 cc) included in the notifications, in the operating statemanagement table of the control apparatus 50 x (steps S47-1 and S47-2).Accordingly, the control apparatus 50 x can detect the operating stateof each terminal (10 bb and 10 cc) serving as a candidate counterpartterminal of the terminal 10 aa connected to the control apparatus 50 x.

In addition, the data processor 59 of the control apparatus 50 x readsout, from the operating state management table, an operating statecorresponding to the terminal ID of the terminal 10 aa connected to thecontrol apparatus 50 x (step S48). The transmitter/receiver 51 of thecontrol apparatus 50 x transmits a notification including the terminalID of the terminal 10 aa and the operating state read out in step S48 tothe control apparatuses (50 y and 50 z) that are connection destinationsof the terminals (10 bb and 10 cc) serving as candidate counterpartterminals (step S49-1 and S49-2). Upon receipt of the notification bythe transmitter/receiver 51 of each control apparatus (50 y and 50 z),the transmitter/receiver 51 transmits the received notification to acorresponding terminal (10 bb or 10 cc) connected to the local controlapparatus (steps S50-1 and S50-2). Upon receipt of the notification bythe transmitter/receiver 11 of the terminal (10 bb or 10 cc), thedisplay control 17 updates an icon indicating the operating state of theterminal 10 aa in the candidate list, on the basis of the terminal IDand operating state of the terminal 10 aa, included in the notification(steps S51-1 and S51-2).

In each of the control apparatuses (50 y and 50 z), on the basis of arequest from the manager 53, the data processor 59 updates the operatingstate of the terminal 10 aa in the operating state management table inthe local control apparatus, on the basis of the notificationtransmitted from the control apparatus 50 x (step S52-1 or S52-2).Accordingly, each of the control apparatuses (50 y and 50 z) can detectthe operating state of the terminal 10 aa connected to the controlapparatus 50 x.

Whenever the operating state of a terminal 10 connected to a localcontrol apparatus 50 is updated, each control apparatus 50 and eachterminal 10 repeat the operation in steps S43-1 to S47-1, the operationin steps S43-2 to S47-2, or the operation in steps S48 to S52-1 andS52-2. Accordingly, each control apparatus 50, each terminal 10, or theuser of each terminal 10 can detect the most recent operating state ofeach terminal 10.

(Establishment of Session Sed)

Next, using FIGS. 13A and 13B (FIG. 13), an operation of transmittinginformation between terminals 10 for establishing a session sed will bedescribed. FIG. 13 is a sequence diagram illustrating an operation oftransmitting information between terminals 10. Hereinafter, the casewhere the terminal 10 aa connected to the control apparatus 50 x sends acommunication start request to the terminal 10 bb connected to thecontrol apparatus 50 y will be described.

In response to operation of the operation keys 108 by the user, thetransmitter/receiver 11 of the terminal 10 aa transmits a communicationstart request to the control apparatus 50 x (step S61). Thecommunication start request includes the terminal ID “01aa” of theterminal 10 aa, which is the communication start request sender, and theterminal ID “01bb” of the terminal 10 bb serving as a counterpartterminal.

Upon receipt, by the transmitter/receiver 51 of the control apparatus 50x, of the start request, the data processor 59 stores, on the basis of arequest from the manager 53, the operating state “online(communicating)” in association with the terminal ID of the terminal 10aa, which is the start request sender, in the operating state managementtable (see FIG. 9F) (step S62). The updated operating state “online(communicating)” is reported to a terminal(s) 10 serving as a candidatecounterpart terminal(s) of the terminal 10 aa by the processing inabove-described steps S48 to S51-1 and S51-2.

In addition, the manager 53 manages the communication state of eachterminal 10 in accordance with the rules of the state transitionillustrated by the state transition diagram of FIG. 2 (step S63-1). Thatis, on the basis of the start request received by the control apparatus50 x in step S61, the manager 53 determines state information indicatingthe new state of the terminal 10 aa, which is the start request sender,as “Inviting”, and determines state information indicating the new stateof the terminal 10 bb, which is the counterpart terminal, as “Invited”.The manager 53 transmits to the shared management apparatus 60 aterminal management table updating request including the items of stateinformation “Inviting” and “Invited” indicating the new states of theterminals (10 aa and 10 bb), which are the start request sender and thecounterpart terminal, in association with the terminal IDs of theterminals (10 aa and 10 bb).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal IDs and the items of stateinformation, which are included in the updating request, in the terminalmanagement table (see FIG. 9B) on the shared management apparatus 60side. Thereafter, by executing the same processing as steps S8-2-1,S8-2- . . . , the terminal management table on each control apparatus(50 x, 50 y, and 50 z) side is synchronized with the terminal managementtable on the shared management apparatus 60 side (steps S63-2-1,S63-2-2, S63-2- . . . in FIG. 13B).

Next, the session control 58 selects a relay device 30 that serves asthe origin in a session sed, from the relay devices (30 xx and 30 yy)connected to the terminals (10 aa and 10 bb) (step S64). In a sessionsed to be established between the terminals (10 aa and 10 bb), the tworelay devices (30 xx and 30 yy) relay content data. Out of the relaydevices (30 xx and 30 yy), a relay device 30 selected in step S64manages the entirety of a relay destination (counterpart terminal) ofcontent data in a session between nodes (terminals 10 or relay devices30). That is, the selected relay device 30 serves as the origin toprovide the other relay device(s) 30 with information indicating a relaydestination of content data. The method of selecting a relay device 30in step S64 is not particularly limited. In the embodiment, thedescription will be continuously given, assuming that the relay device30 xx to which the terminal 10 aa that is the start request sender isconnected is selected.

Next, the manager 53 manages information regarding a session sed to beestablished between the terminals (10 aa and 10 bb) (step S65-1). Atfirst, the manager 53 generates a session ID for identifying a sessionsed to be established between the terminals (10 aa and 10 bb). In thiscase, the manager 53 generates a session ID (such as “conf01.001xx”)including information (such as “001xx”) indicating the relay device 30xx serving as the origin, selected in step S64. Next, on the basis of arequest from the manager 53, the transmitter/receiver 61 of the sharedmanagement apparatus 60 transmits, to the shared management apparatus60, a request for updating the session management table (see FIG. 9D),including the generated session ID, and the terminal IDs of theterminals (10 aa and 10 bb), which are the start request sender and thecounterpart terminal.

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the session ID and the terminal IDs, which areincluded in the updating request, in the session management table on theshared management apparatus 60 side. Thereafter, thetransmitter/receiver 61 transmits the updated details of the sessionmanagement table to the control apparatuses (50 x, 50 y, and 50 z)included in the communication system 1. Upon receipt of the updateddetails by the transmitter/receiver 51 of each control apparatus (50 x,50 y, and 50 z), the data processor 59 of each control apparatus 50updates the session management table therein on the basis of the updateddetails. Accordingly, the session management table on each controlapparatus (50 x, 50 y, and 50 z) side is synchronized with the sessionmanagement table on the shared management apparatus 60 side (stepsS65-2-1, S65-2- . . . ).

In addition, the transmitter/receiver 51 of the control apparatus 50 xtransmits the session ID, generated in step S65-1, to the terminal 10aa, which is the start request sender (step S66). Furthermore, thetransmitter/receiver 51 of the control apparatus 50 x transmits thestart request, transmitted from the terminal 10 aa, which is the startrequest sender, and the above-mentioned session ID to the terminal 10bb, which is the counterpart terminal (step S67). Note that the terminalmanagement table (see FIG. 9B) on the control apparatus 50 x side issynchronized with the terminal management table on the shared managementapparatus 60 side on the basis of the IP address of the terminal 10 bb,transmitted from the shared management apparatus 60, and manages the IPaddress of the terminal 10 bb, which is the counterpart terminal.Therefore, the transmitter/receiver 51 of the control apparatus 50 x candirectly transmit the start request or the like to the terminal 10 bb,without sending an inquiry about the IP address to the control apparatus50 y, which is a connection destination of the terminal 10 bb, which isthe counterpart terminal, or without having the control apparatus 50 ytherebetween.

Upon receipt, by the transmitter/receiver 11 of the terminal 10 bb,which is the counterpart terminal, of the start request, thecommunication control 13 causes the speaker 115 to output a ringtone.Next, the transmitter/receiver 11 of the terminal 10 bb transmitsringing information indicating that a ringtone is being output, to thecontrol apparatus 50 y, which is a connection destination of theterminal 10 bb (step S68). The ringing information includes the terminalIDs of the terminals (10 aa and 10 bb), which are the start requestsender and the counterpart terminal.

Upon receipt of the ringing information by the transmitter/receiver 51of the control apparatus 50 y, the manager 53 manages the communicationstate of each terminal 10 in accordance with the rules of the statetransition illustrated by the state transition diagram of FIG. 2 (stepS69-1). That is, on the basis of the ringing information received by thecontrol apparatus 50 y in step S68, the manager 53 determines stateinformation indicating the new state of the terminal 10 aa, which is thestart request sender, as “Calling”, and determines state informationindicating the new state of the terminal 10 bb, which is the counterpartterminal, as “Ringing”. The manager 53 transmits to the sharedmanagement apparatus 60 a terminal management table updating requestincluding the items of state information “Calling” and “Ringing”indicating the new states of the terminals (10 aa and 10 bb), which arethe start request sender and the counterpart terminal, in associationwith the terminal IDs of the terminals (10 aa and 10 bb).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal IDs and the items of stateinformation, which are included in the updating request, in the terminalmanagement table (see FIG. 9B) on the shared management apparatus 60side. Thereafter, by executing the same processing as steps S8-2-1,S8-2- . . . , the terminal management table on each control apparatus(50 x, 50 y, and 50 z) side is synchronized with the terminal managementtable on the shared management apparatus 60 side (steps S69-2-1,S69-2-2, S69-2- . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 ytransmits the ringing information, transmitted from the terminal 10 bb,which is the counterpart terminal, to the terminal 10 aa, which is thestart request sender (step S70). Since the terminal management table(see FIG. 9B) on the control apparatus 50 y side is synchronized withthe terminal management table on the shared management apparatus 60 sideon the basis of information transmitted from the shared managementapparatus 60, the terminal management table on the control apparatus 50y side manages the IP address of the terminal 10 aa, which is the startrequest sender. Therefore, the transmitter/receiver 51 of the controlapparatus 50 y can directly transmit the ringing information to theterminal 10 aa, without sending an inquiry about counterpart terminalinformation to the control apparatus 50 x, which is a connectiondestination of the terminal 10 aa, or without having the controlapparatus 50 x therebetween.

In contrast, in the terminal 10 bb, which is the counterpart terminal,upon receipt by the acceptor 12 of a communication start permission onthe basis of an input operation performed by the user, thetransmitter/receiver 11 transmits start permission informationindicating a communication start permission to the control apparatus 50y, which is a connection destination of the terminal 10 bb (step S71).The start permission information includes the terminal IDs of theterminals (10 aa and 10 bb), which are the start request sender and thecounterpart terminal.

Upon receipt of the start permission information by thetransmitter/receiver 51 of the control apparatus 50 y, the manager 53determines, on the basis of the received start permission information,items of state information indicating the new states of the terminals(10 aa and 10 bb), which are the start request sender and thecounterpart terminal, as “Accepted”, by executing the same processing asstep S69-1. The manager 53 transmits to the shared management apparatus60 a terminal management table updating request including the items ofstate information “Accepted” indicating the new states of the terminals(10 aa and 10 bb), which are the start request sender and thecounterpart terminal (step S72-1).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal IDs and the items of stateinformation, which are included in the updating request, in the terminalmanagement table (see FIG. 9B) on the shared management apparatus 60side. Thereafter, by executing the same processing as steps S8-2-1,S8-2- . . . , the terminal management table on each control apparatus(50 x, 50 y, and 50 z) side is synchronized with the terminal managementtable on the shared management apparatus 60 side (steps S72-2-1,S72-2-2, S72-2- . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 ytransmits the start permission information, transmitted from theterminal 10 bb, which is the counterpart terminal, to the terminal 10aa, which is the start request sender, by executing the same processingas step S70 (step S73).

Next, using FIGS. 14A and 14B (FIG. 14), an operation in which theterminals (10 aa and 10 bb), which are the start request sender and thecounterpart terminal, request the relay devices (30 xx and 30 yy),serving as connection destinations of the terminals (10 aa and 10 bb),respectively, to start relaying content data will be described. FIGS.14A and 14B are sequence diagrams illustrating an operation of startingrelaying content data.

Using FIG. 14A, an operation of establishing a session sed between theterminal 10 aa and the relay device 30 xx in order to start relayingcontent data between the terminals (10 aa and 10 bb) will be described.After having received the start permission information (see step S73),the transmitter/receiver 11 of the terminal 10 aa, which is the startrequest sender, transmits to the control apparatus 50 x relay requestinformation indicating a request for starting relaying content data(step S81). The relay request information includes the terminal ID ofthe terminal 10 aa, which is the relay request sender, and the sessionID “conf01.001xx” received in step S66.

Upon receipt of the relay request information by thetransmitter/receiver 51 of the control apparatus 50 x, the manager 53determines, on the basis of the received relay request information,state information indicating the new state of the terminal 10 aa, whichis the relay request sender, as “Busy”, by executing the same processingas step S63-1. The manager 53 transmits to the shared managementapparatus 60 a terminal management table updating request including theterminal ID of the terminal 10 aa, which is the relay request sender,and the state information “Busy” indicating the new state of theterminal 10 aa (step S82-1).

Upon receipt of these items of information by the transmitter/receiver61 of the shared management apparatus 60, the data processor 69associatively stores the terminal ID and the state information, whichare included in the updating request, in the terminal management table(see FIG. 9B) on the shared management apparatus 60 side. By executingthe same processing as steps S8-2-1, S8-2- . . . , the terminalmanagement table on each control apparatus (50 x, 50 y, and 50 z) sideis synchronized with the terminal management table on the sharedmanagement apparatus 60 side (steps S82-2-1, S82-2 . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 xtransmits, on the basis of the relay device ID “001xx” associated withthe terminal ID of the terminal 10 aa, which is the relay requestsender, in the terminal management table (see FIG. 9B) in the controlapparatus 50 x, the relay request information, transmitted from theterminal 10 aa, which is the relay request sender, to the relay device30 xx identified by the relay device ID “001xx” (step S83). In responseto the relay request information, the transmitter/receiver 31 of therelay device 30 xx transmits relay permission information indicating arelaying permission to the control apparatus 50 x (step S84). Uponreceipt of the relay permission information transmitted from the relaydevice 30 xx, the transmitter/receiver 51 of the control apparatus 50 xtransmits the relay permission information to the terminal 10 aa, whichis the relay request sender (step S85).

Upon receipt of the relay request information by thetransmitter/receiver 31 of the relay device 30 xx, the relay device 30xx side can detect that the terminal 10 aa, which is the relay requestsender, will participate in a session identified by the session IDincluded in the relay request information. Accordingly, the relay device30 xx starts relaying content data transmitted from the terminal 10 aato another terminal 10 participating in the same session as the terminal10 aa, and starts transmitting content data transmitted from this otherterminal to the terminal 10 aa. In this manner, a session sed isestablished between the terminal 10 aa and the relay device 30 xx.

Next, using FIG. 14B, an operation of establishing a session sed betweenthe terminal 10 bb and the relay device 30 yy and between the relaydevices (30 xx and 30 yy) in order to start relaying content databetween the terminals (10 aa and 10 bb) will be described. After havingtransmitted the start permission information (see step S71), thetransmitter/receiver 11 of the terminal 10 bb transmits to the controlapparatus 50 y relay request information indicating a request forstarting relaying content data (step S91). The relay request informationincludes the terminal ID of the terminal 10 bb, which is the relayrequest sender, and the session ID “conf01.001xx” received in step S67.

Upon receipt of the relay request information by thetransmitter/receiver 51 of the control apparatus 50 y, the manager 53determines, on the basis of the received relay request information,state information indicating the new state of the terminal 10 bb, whichis the relay request sender, as “Busy”, by executing the same processingas step S69-1. The manager 53 transmits to the shared managementapparatus 60 a terminal management table updating request including theterminal ID of the terminal 10 bb, which is the relay request sender,and the state information “Busy” indicating the new state of theterminal 10 bb (step S92-1).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal ID and the state information, whichare included in the updating request, in the terminal management table(see FIG. 9B) on the shared management apparatus 60 side. Thereafter, byexecuting the same processing as steps S8-2-1, S8-2- . . . , theterminal management table on each control apparatus (50 x, 50 y, and 50z) side is synchronized with the terminal management table on the sharedmanagement apparatus 60 side (steps S92-2-1, S92-2 . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 ytransmits, on the basis of the relay device ID “001yy” associated withthe terminal ID of the terminal 10 bb, which is the relay requestsender, in the terminal management table (see FIG. 9B) in the controlapparatus 50 y, the relay request information, transmitted from theterminal 10 bb, which is the relay request sender, to the relay device30 yy identified by the relay device ID “001yy” (step S93). Since thesession ID “conf01.001xx” included in the relay request informationincludes the information “001xx” indicating the relay device 30 xxserving as the origin, the relay device 30 yy side which has receivedthe relay request information can detect that the relay device 30serving as the origin in this session sed is the relay device 30 xx.Therefore, the transmitter/receiver 31 of the relay device 30 yytransmits the relay request information, transmitted from the controlapparatus 50 y, to the relay device 30 xx serving as the origin (stepS94).

In response to the relay request information, the transmitter/receiver31 of the relay device 30 xx transmits relay permission informationindicating a relaying permission to the relay device 30 yy (step S95).In response to the relay request information, the transmitter/receiver31 of the relay device 30 yy transmits relay permission informationindicating a relaying permission to the control apparatus 50 y (stepS96). Upon receipt of the relay permission information transmitted fromthe relay device 30 yy, the transmitter/receiver 51 of the controlapparatus 50 y transmits the relay permission information to theterminal 10 bb, which is the relay request sender (step S97).

Upon receipt of the relay request information by thetransmitter/receiver 31 of the relay device 30 xx, the relay device 30xx side can detect that the terminal 10 bb connected to the relay device30 yy will participate in a session identified by the session IDincluded in the relay request information. On the basis of to whichrelay device 30 each terminal 10 participating in the session sed isconnected, the relay device 30 xx determines a transmission route ofcontent data, and notifies the relay device 30 yy thereof. For example,the relay device 30 xx transmits to the relay device 30 yy a request fortransmitting content data transmitted from the terminal 10 bb to therelay device 30 xx and transmitting content data transmitted from therelay device 30 xx to the terminal 10 bb. Accordingly, the relay device30 yy starts transmitting content data, transmitted from the terminal 10bb, to the relay device 30 xx, and starts transmitting content data ofthe terminal 10 aa, transmitted from the relay device 30 xx, to theterminal 10 bb. In this manner, a session sed is established between theterminal 10 bb and the relay device 30 yy and between the relay devices(30 xx and 30 yy).

When the session sed is established between the terminal 10 aa and therelay device 30 xx, between the terminal 10 bb and the relay device 30yy, and between the relay devices (30 xx and 30 yy), content data can betransmitted to and from the terminals (10 aa and 10 bb).

Next, using FIGS. 15A and 15B (FIG. 15), after the session sed isestablished between the terminal 10 aa and the relay device 30 xx,between the terminal 10 bb and the relay device 30 yy, and between therelay devices (30 xx and 30 yy), an operation where the terminal 10 ccconnected to the relay device 30 zz participates in the above-describedsession sed will be described. FIG. 15 is a sequence diagramillustrating an operation where the terminal 10 cc participates in thesession sed.

At first, in the terminal 10 aa participating in the session sed, uponreceipt by the acceptor 12 of a request from the user for inviting theterminal 10 cc to the session sed, the transmitter/receiver 11 transmitsinvitation information for inviting the terminal 10 cc to the sessionsed, to the control apparatus 50 x, which is a connection destination ofthe terminal 10 aa (step S101). The invitation information includes thesession ID of the session sed, and the terminal ID of the terminal 10 ccto be invited.

Upon receipt of the invitation information transmitted from the terminal10 aa, the transmitter/receiver 51 of the control apparatus 50 xtransmits the invitation information to the terminal 10 cc, on the basisof the terminal ID included in the invitation information (step S102).Note that the terminal management table (see FIG. 9B) on the controlapparatus 50 x side is synchronized with the terminal management tableon the shared management apparatus 60 side on the basis of theinformation transmitted from the shared management apparatus 60, andmanages the IP address of the terminal 10 cc, which is the counterpartterminal. Therefore, the transmitter/receiver 51 of the controlapparatus 50 x can directly transmit the invitation information to theterminal 10 cc, without sending an inquiry about counterpart terminalinformation to the control apparatus 50 z, which is a connectiondestination of the terminal 10 cc, or without having the controlapparatus 50 z therebetween.

Upon receipt of the invitation information transmitted from the controlapparatus 50 x, the transmitter/receiver 11 of the terminal 10 cctransmits, on the basis of a request from the user, participationrequest information indicating a request for participating in thesession sed, which has been invited by the terminal 10 aa side, to thecontrol apparatus 50 z, which is a connection destination of theterminal 10 cc (step S103). The participation request informationincludes the session ID of the session sed to participate.

Upon receipt of the participation request information by thetransmitter/receiver 51 of the control apparatus 50 z, the manager 53determines, on the basis of the received participation requestinformation, state information indicating the new state of the terminal10 cc, which is the participation request sender, as “Accepted” byexecuting the same processing as step S63-1. The manager 53 transmits tothe shared management apparatus 60 a terminal management table updatingrequest including the terminal ID of the terminal 10 cc, which is theparticipation request sender, and the state information “Accepted”indicating the new state of the terminal 10 cc (step S104-1).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal ID and the state information, whichare included in the updating request, in the terminal management table(see FIG. 9B) on the shared management apparatus 60 side. By executingthe same processing as steps S8-2-1, S8-2- . . . , the terminalmanagement table on each control apparatus (50 x, 50 y, and 50 z) sideis synchronized with the terminal management table on the sharedmanagement apparatus 60 side (steps S112-2-1, S112-2 . . . ).

Next, the manager 53 manages information regarding the session sedestablished among the terminals (10 aa, 10 bb, and 10 cc) (step S105-1).In this case, on the basis of a request from the manager 53, thetransmitter/receiver 51 transmits, to the shared management apparatus60, a request for updating the session management table, including thesession ID, and the terminal ID of the terminal 10 cc serving as theparticipation request sender, which are included in the participationrequest information.

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the session ID and the terminal ID, which areincluded in the updating request, in the session management table (seeFIG. 9D) on the shared management apparatus 60 side. Thereafter, byexecuting the same processing as steps S65-2-1, S65-2, . . . , thesession management table on each control apparatus (50 x, 50 y, and 50z) side is synchronized with the session management table on the sharedmanagement apparatus 60 side (steps S105-2- . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 ztransmits participation permission information indicating aparticipation permission to the terminal 10 cc, which is theparticipation request sender (step S106).

After having received the participation permission information, thetransmitter/receiver 11 of the terminal 10 cc, which is theparticipation request sender, transmits to the control apparatus 50 zrelay request information indicating a request for starting relayingcontent data (step S111). The relay request information includes theterminal ID of the terminal 10 cc, which is the relay request sender,and the session ID “conf01.001xx” received in step S102.

Upon receipt of the relay request information by thetransmitter/receiver 51 of the control apparatus 50 z, the manager 53determines, on the basis of the received relay request information,state information indicating the new state of the terminal 10 cc, whichis the relay request sender, as “Busy”, by executing the same processingas step S63-1. The manager 53 transmits to the shared managementapparatus 60 a terminal management table updating request including theterminal ID of the terminal 10 cc, which is the relay request sender,and the state information “Busy” indicating the new state of theterminal 10 cc (step S112-1).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal ID and the state information, whichare included in the updating request, in the terminal management table(see FIG. 9B) on the shared management apparatus 60 side. Next, byexecuting the same processing as steps S8-2-1, S8-2- . . . , theterminal management table on each control apparatus (50 x, 50 y, and 50z) side is synchronized with the terminal management table on the sharedmanagement apparatus 60 side (steps S112-2-1, S112-2 . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 ztransmits, on the basis of the relay device ID “001zz” associated withthe terminal ID of the terminal 10 cc, which is the relay requestsender, in the terminal management table (see FIG. 9B) in the controlapparatus 50 z, the relay request information, transmitted from theterminal 10 cc, which is the relay request sender, to the relay device30 zz identified by the relay device ID “001zz” (step S113). The relayrequest information additionally includes the terminal ID of theterminal 10 cc, which is the participation request sender, in additionto the relay request information sent from the terminal 10 cc.

Since the session ID “conf01.001xx” included in the relay requestinformation includes the information “001xx” indicating the relay device30 serving as the origin, the relay device 30 zz side which has receivedthe relay request information can detect that the relay device 30serving as the origin in this session sed is the relay device 30 xx.Therefore, the transmitter/receiver 31 of the relay device 30 zztransmits the relay request information, transmitted from the controlapparatus 50 z, to the relay device 30 xx serving as the origin (stepS114).

In response to the relay request information, the transmitter/receiver31 of the relay device 30 xx transmits relay permission informationindicating a relaying permission to the relay device 30 zz (step S115).In response to the relay request information, the transmitter/receiver31 of the relay device 30 zz transmits relay permission informationindicating a relaying permission to the control apparatus 50 z (stepS116). Upon receipt of the relay permission information transmitted fromthe relay device 30 zz, the transmitter/receiver 51 of the controlapparatus 50 z transmits the relay permission information to theterminal 10 cc, which is the relay request sender (step S117).

Upon receipt of the relay request information by thetransmitter/receiver 31 of the relay device 30 xx, the relay device 30xx side can detect that the terminal 10 cc connected to the relay device30 zz will participate in a session identified by the session IDincluded in the relay request information. On the basis of to whichrelay device 30 each terminal 10 participating in the session sed isconnected, the relay device 30 xx determines a transmission route ofcontent data, and notifies the relay devices (30 zz and 30 yy) thereof.For example, the relay device 30 xx transmits to the relay device 30 zza request for transmitting content data transmitted from the terminal 10cc to the relay devices (30 xx and 30 yy) and transmitting content dataof the terminals (10 aa and 10 bb), transmitted from the relay devices(30 xx and 30 zz), to the terminal 10 cc. Accordingly, the relay device30 zz starts transmitting content data, transmitted from the terminal 10cc, to the relay devices (30 xx and 30 yy), and starts transmittingcontent data of the terminals 10 aa and 10 bb, transmitted from therelay devices 30 xx and 30 yy, to the terminal 10 bb.

In addition, the relay device 30 xx transmits to the relay device 30 yya request for transmitting content data transmitted from the terminal 10bb to the relay device 30 zz and transmitting content data of theterminal 10 cc, transmitted from the relay device 30 zz, to the terminal10 bb. Accordingly, the relay device 30 yy starts transmitting contentdata, transmitted from the terminal 10 bb, to the relay device 30 zz,and starts transmitting content data of the terminal 10 cc, transmittedfrom the relay device 30 zz, to the terminal 10 bb.

In this manner, a session sed is established between the terminal 10 ccand the relay device 30 zz and between the relay device 30 zz and therelay devices (30 xx and 30 yy).

When the session sed is established between the terminal 10 cc and therelay device 30 zz, and between the relay device 30 zz and the relaydevices (30 xx and 30 yy), content data can be transmitted among theterminals (10 aa, 10 bb, and 10 cc).

(Exit from Session Sed)

Next, using FIG. 16A, an operation where the terminal 10 aa, which isparticipating in the session sed established among the terminals (10 aa,10 bb, and 10 cc), exits from the session sed will be described. FIG.16A is a sequence diagram illustrating an operation where the terminal10 aa exits from the session sed.

At first, the transmitter/receiver 11 of the terminal 10 aa transmits,on the basis of a request from the user, end request informationindicating a request for ending communication to the control apparatus50 x (step S121). The end request information includes the session ID“conf01.001xx” of the session sed in which the terminal 10 aa isparticipating.

Upon receipt of the end request information by the transmitter/receiver51 of the control apparatus 50 x, the manager 53 determines, on thebasis of the received end request information, state informationindicating the new state of the terminal 10 aa, which is the end requestsender, as “None”, by executing the same processing as step S63-1. Themanager 53 transmits to the shared management apparatus 60 a terminalmanagement table updating request including the terminal ID of theterminal 10 aa, which is the end request sender, and the stateinformation “None” indicating the new state of the terminal 10 aa (stepS122-1).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal ID and the state information, whichare included in the updating request, in the terminal management table(see FIG. 9B) on the shared management apparatus 60 side. By executingthe same processing as steps S8-2-1, S8-2- . . . , the terminalmanagement table on each control apparatus (50 x, 50 y, and 50 z) sideis synchronized with the terminal management table on the sharedmanagement apparatus 60 side (steps S122-2-1, S122-2 . . . ).

Next, the manager 53 manages information regarding the session sed fromwhich the terminal 10 aa will exit (step S123-1). In this case, on thebasis of a request from the manager 53, the transmitter/receiver 51transmits, to the shared management apparatus 60, a request for updatingthe session management table, including the session ID included in theend request information, and the terminal ID of the terminal 10 aa,which will exit from the session sed.

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69 deletes theterminal ID of the terminal 10 aa, associated with the session IDincluded in the updating request, from the session management table (seeFIG. 9D) on the shared management apparatus 60 side. Thereafter, byexecuting the same processing as steps S65-2-1, S65-2-, . . . , thesession management table on each control apparatus (50 x, 50 y, and 50z) side is synchronized with the session management table on the sharedmanagement apparatus 60 side (steps S123-2- . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 xtransmits, on the basis of the relay device ID “001xx” associated withthe terminal ID of the terminal 10 aa, which is the end request sender,in the terminal management table (see FIG. 9B) in the control apparatus50 x, the end request information, transmitted from the terminal 10 aa,which is the end request sender, to the relay device 30 xx identified bythe relay device ID “001xx” (step S124).

Upon receipt of the end request information by the transmitter/receiver31 of the relay device 30 xx, the relay device 30 xx side can detectthat the terminal 10 aa will exit from the session sed established amongthe terminals (10 aa, 10 bb, and 10 cc). On the basis of to which relaydevice 30 each of terminals (10 bb and 10 cc) participating in thesession sed is connected after the terminal 10 aa exits from the sessionsed, the relay device 30 xx determines a transmission route of contentdata, and notifies the relay devices (30 yy and 30 zz) thereof. Forexample, the relay device 30 xx transmits to the relay device 30 yy arequest for transmitting content data transmitted from the terminal 10bb to the relay device 30 zz and transmitting content data of theterminal 10 cc, transmitted from the relay device 30 zz, to the terminal10 bb. In addition, the relay device 30 xx transmits to the relay device30 zz a request for transmitting content data transmitted from theterminal 10 cc to the relay device 30 yy, and transmitting content dataof the terminal 10 bb, transmitted from the relay device 30 yy, to theterminal 10 cc.

Accordingly, the terminal 10 aa is disconnected from the session sed(step S125), while the terminals (10 bb and 10 cc) can continuouslytransmit content data to and from each other.

Next, using FIG. 16B, an operation where, after the terminal 10 aaexits, the terminal 10 bb exits from the session sed established betweenthe terminals (10 bb and 10 cc) will be described. At first, thetransmitter/receiver 11 of the terminal 10 bb transmits, on the basis ofa request from the user, end request information indicating a requestfor ending communication to the control apparatus 50 y (step S131). Theend request information includes the session ID “conf01.001xx” of thesession sed in which the terminal 10 bb is participating.

Upon receipt of the end request information by the transmitter/receiver51 of the control apparatus 50 y, the manager 53 determines, on thebasis of the received end request information, state informationindicating the new state of the terminal 10 bb, which is the end requestsender, as “None”, by executing the same processing as step S63-1. Themanager 53 transmits to the shared management apparatus 60 a terminalmanagement table updating request including the terminal ID of theterminal 10 bb, which is the end request sender, and the stateinformation “None” indicating the new state of the terminal 10 bb (stepS132-1).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69associatively stores the terminal ID and the state information, whichare included in the updating request, in the terminal management table(see FIG. 9B) on the shared management apparatus 60 side. Thereafter, byexecuting the same processing as steps S8-2-1, S8-2- . . . , theterminal management table on each control apparatus (50 x, 50 y, and 50z) side is synchronized with the terminal management table on the sharedmanagement apparatus 60 side (steps S132-2-1, S132-2 . . . ).

Next, the manager 53 manages information regarding the session sed fromwhich the terminal 10 bb will exit (step S133-1). In this case, on thebasis of a request from the manager 53, the transmitter/receiver 51transmits, to the shared management apparatus 60, a request for updatingthe session management table, including the session ID included in theend request information, and the terminal ID of the terminal 10 bb,which will exit from the session sed.

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of the updating request, the data processor 69 deletes theterminal ID of the terminal 10 bb, associated with the session IDincluded in the updating request, from the session management table (seeFIG. 9D) on the shared management apparatus 60 side. Thereafter, byexecuting the same processing as steps S65-2-1, S65-2-, . . . , thesession management table on each control apparatus (50 x, 50 y, and 50z) side is synchronized with the session management table on the sharedmanagement apparatus 60 side (steps S133-2- . . . ).

Next, the transmitter/receiver 51 of the control apparatus 50 ytransmits, on the basis of the relay device ID “001yy” associated withthe terminal ID of the terminal 10 bb, which is the end request sender,in the terminal management table (see FIG. 9B) in the control apparatus50 y, the relay request information, transmitted from the terminal 10bb, which is the end request sender, to the relay device 30 yyidentified by the relay device ID “001yy” (step S134). Since the sessionID “conf01.001xx” included in the end request information includes theinformation “001xx” indicating the relay device 30 xx serving as theorigin, the relay device 30 yy side which has received the relay requestinformation can detect that the relay device 30 serving as the origin inthis session sed is the relay device 30 xx. Therefore, thetransmitter/receiver 31 of the relay device 30 yy transmits the endrequest information, transmitted from the control apparatus 50 y, to therelay device 30 xx serving as the origin (step S135).

Upon receipt of the end request information by the transmitter/receiver31 of the relay device 30 xx, the relay device 30 xx side can detectthat the terminal 10 bb will exit from the session sed establishedbetween the terminals (10 bb and 10 cc). On the basis of to which relaydevice 30 the terminal 10 cc participating in the session sed isconnected after the terminal 10 bb exits from the session sed, the relaydevice 30 xx determines a transmission route of content data, andnotifies the relay devices (30 yy and 30 zz) thereof. For example, therelay device 30 xx transmits to the relay device 30 yy a request fordisconnecting the session sed with the terminal 10 bb and with the relaydevice 30 xx. In addition, the relay device 30 xx transmits to the relaydevice 30 zz a request for transmitting content data of the terminal 10cc, transmitted from the terminal 10 cc, back to the content data 10 cc.Accordingly, the terminal 10 bb is disconnected from the session sed(step S137), while the terminal 10 bb can continue the session sed forreceiving, by itself via the relay device 30 zz, content data that hasbeen transmitted by itself.

(Log Out Operation)

First, using FIG. 17, an operation where a terminal 10 logs out from acontrol apparatus 50 will be described. FIG. 17 is a sequence diagramillustrating a logout operation of a terminal 10. Hereinafter, anoperation where, after exiting from the session sed with the terminals(10 bb and 10 cc), the terminal 10 aa logs out from the controlapparatus 50 x will be described.

On the basis of a request from the user, the transmitter/receiver 11 ofthe terminal 10 aa transmits a logout request to the control apparatus50 x (step S141). Upon receipt of the logout request, thetransmitter/receiver 51 of the control apparatus 50 x transmits, on thebasis of a request from the manager 53, a request for deleting, from theterminal management table (see FIG. 9B), an area ID, IP address, andrelay device ID associated with the terminal ID of the terminal 10 aawhich will log out, to the shared management apparatus 60 (step S142-1).

Upon receipt, by the transmitter/receiver 61 of the shared managementapparatus 60, of this request, the data processor 69 deletes an area ID,IP address, and relay device ID associated with the received terminalID, from the terminal management table (see FIG. 9B) on the sharedmanagement apparatus 60 side. Thereafter, by executing the sameprocessing as steps S8-2-1, S8-2- . . . , the terminal management tableon each control apparatus (50 x, 50 y, and 50 z) side is synchronizedwith the terminal management table on the shared management apparatus 60side (step S142-2 . . . ).

Next, on the basis of a request from the manager 53, the data processor59 stores the operating state “offline” in association with the terminalID of the terminal 10 aa, which is the logout request sender, in theoperating state management table (see FIG. 9F) (step S143). The updatedoperating state “offline” is reported to a terminal(s) 10 serving as acandidate counterpart terminal(s) of the terminal 10 aa by theprocessing in above-described steps S48 to S51-1 and S51-2.

In addition, the manager 53 deletes each record where the terminal ID ofthe terminal 10 aa, which is the logout request sender, is recorded,from the connection management table (FIG. 9G) of the control apparatus50 x (step S144). Accordingly, the terminal ID of the terminal 10 aa,and a relay device connection ID and a relay device connection passwordthat are associated with this terminal ID are deleted from theconnection management table.

Next, the transmitter/receiver 51 of the control apparatus 50 xtransmits logout completion information indicating that logout has beencompleted to the terminal 10 aa, which is the logout request sender(step S145).

In addition, the terminal 10 aa transmits a logout request to the relaydevice 30 xx (step S146). Upon completion of operation involved inlogging out of the terminal 10 aa, the relay device 30 xx transmitslogout completion information to the terminal 10 aa (step S147).

With the above operation, the terminal 10 aa completely logs out fromthe control apparatus 50 x and the relay device 30 xx.

The control system 5 includes a plurality of control apparatuses 50 eachcapable of controlling a session sed for transmitting content databetween at least two terminals 10 of a first terminal 10 and a secondterminal 10. In establishing a session sed for transmitting content datathrough a plurality of relay devices, the session control 58 determinesone of the plurality of relay devices 30, as a representative relaydevice (referred to as the origin relay device in the above description)to manage a relay destination of content data in the session sed (SeeS64) when established.

In response to a request for starting relay of content data through thesession sed from a terminal 10, the transmitter/receiver 51 (an exampleof transmitter) transmits, with the request for starting relay ofcontent data, a relay device ID (an example of identificationinformation) of the representative relay device to at least one relaydevice 30 that connects to the requesting terminal 10. The relay device30 that receives the representative relay device ID is caused to furthertransmit the request to the representative relay device identified withthe received representative relay device ID. For example, if the relaydevice 30 receiving the representative relay device ID is therepresentative relay device 30 itself, the representative relay device30 does not transmit the representative relay device ID to any otherrelay device 30. If the relay device 30 receiving the representativerelay device ID is the relay device 30 other than the representativerelay device, the relay device 30 transmits the representative relaydevice ID to the representative relay device 30.

Accordingly, each relay device 30 is notified of the representativerelay device 30, which manages the session to be established forrelaying content data, such that the each relay device 30 is able tosend the request for starting relay of content data to therepresentative relay device 30.

The representative relay device 30 that manages a relay destination ofcontent data, which receives notification from the relay device 30connected to the requesting terminal 10, is able to determine a route oftransmitting content data to the requesting terminal 10. Even in a casewhere the requesting terminal 10 is connected to the relay device 30,which is not accessible by the control apparatus 50, the representativerelay device 30 is able to transmit content data to the requestingterminal 10 through the relay device 30, as the relay device 30 accessesthe representative relay device 30 using the representative relay deviceID.

The request for starting relay of content data may be transmitted fromany other terminal 10, which may be newly invited to join in the sessionthat is established. In such case, the terminal 10 participating in thesession, which receives the representative relay device ID from thecontrol apparatus 50, sends invitation to the other terminal 10 with therepresentative relay device ID. The other terminal 10 sends a requestfor starting relay of content data with the representative relay deviceID, to a control apparatus 50 managing the other terminal 10. Thecontrol apparatus 50 sends the representative relay device ID to a relaydevice 30 connected to the other terminal 10 that requests for relayingcontent data. The relay device 30 transmits the request for relayingcontent data to the representative relay device 30, which is identifiedwith the received representative relay device ID. The representativerelay device 30 that manages a relay destination of content data, whichreceives notification from the relay device 30 connected to therequesting other terminal 10, is able to determine a route oftransmitting content data to the requesting other terminal 10.

The above-described embodiment has discussed the case where the relaydevice ID of the representative relay device 30 (origin relay device 30)for managing a relay destination of content data, is included as a partof the session ID of the session. However, the present invention is notlimited to the above-described embodiment. For example, as long as therelay device ID of the representative relay device 30 is associated withthe session ID, these data may be independently managed. In such case,the session management table (FIG. 9D) stores the session ID and therelay device ID in separate fields, but in association with each other.Further, each one of the terminal 10, the control apparatus 50, and therelay device 30 transmits the session ID and the relay device ID inassociation with one another, to the other terminal 10, controlapparatus 50, or relay device 30.

Each of the functions of the described embodiments may be implemented byone or more processing circuits or circuitry. Processing circuitryincludes a programmed processor, as a processor includes circuitry. Aprocessing circuit also includes devices such as an application specificintegrated circuit (ASIC) and conventional circuit components arrangedto perform the recited functions.

The present invention can be implemented in any convenient form, forexample using dedicated hardware, or a mixture of dedicated hardware andsoftware. The present invention may be implemented as computer softwareimplemented by one or more networked processing apparatuses. The networkcan comprise any conventional terrestrial or wireless communicationsnetwork, such as the Internet. The processing apparatuses can compromiseany suitably programmed apparatuses such as a general purpose computer,personal digital assistant, mobile telephone (such as a WAP or3G-compliant phone) and so on. Since the present invention can beimplemented as software, each and every aspect of the present inventionthus encompasses computer software implementable on a programmabledevice. The computer software can be provided to the programmable deviceusing any storage medium for storing processor readable code such as afloppy disk, hard disk, CD ROM, magnetic tape device or solid statememory device.

The hardware platform includes any desired kind of hardware resourcesincluding, for example, a central processing unit (CPU), a random accessmemory (RAM), and a hard disk drive (HDD). The CPU may be implemented byany desired kind of any desired number of processor. The RAM may beimplemented by any desired kind of volatile or non-volatile memory. TheHDD may be implemented by any desired kind of non-volatile memorycapable of storing a large amount of data. The hardware resources mayadditionally include an input device, an output device, or a networkdevice, depending on the type of the apparatus. Alternatively, the HDDmay be provided outside of the apparatus as long as the HDD isaccessible. In this example, the CPU, such as a cache memory of the CPU,and the RAM may function as a physical memory or a primary memory of theapparatus, while the HDD may function as a secondary memory of theapparatus.

The invention claimed is:
 1. A control system, comprising: a firstcontrol apparatus including: processing circuitry configured to obtaininformation regarding a plurality of relay devices for relaying contentdata in a session to be established among a plurality of communicationterminals, and determine one of the plurality of relay devices as arepresentative relay device to manage a relay destination of contentdata in the session to be established; and a transmitter configured totransmit relay device identification information for identifying therepresentative relay device to the plurality of communication terminalssubject for participation in the session; and a second control apparatusincluding: a receiver configured to receive, from a first communicationterminal of the plurality of communication terminals subject forparticipation in the session, a request for starting relay of contentdata including the relay device identification information of therepresentative relay device; and a transmitter configured to transmit,with the request for starting relay of content data, the relay deviceidentification information of the representative relay device to a firstrelay device connected to the first communication terminal, to cause thefirst relay device to further transmit the request for starting relay ofcontent data to the representative relay device identified with therelay device identification information of the representative relaydevice.
 2. The control system of claim 1, further comprising: a thirdcontrol apparatus including; a receiver configured to receive, from asecond communication terminal, an other request for starting relay ofcontent data including the relay device identification information ofthe representative relay device, the second communication terminal beinga terminal other than the plurality of communication terminals subjectfor participation in the session; and a transmitter configured totransmit the other request for starting relay of content data to asecond relay device connected to the second communication terminal, tocause the second relay device to further transmit the other request forstarting relay of content data to the representative relay deviceidentified with the relay device identification information of therepresentative relay device.
 3. The control system of claim 1, whereinthe transmitter of the first control apparatus transmits the relaydevice identification information of the representative relay device tothe plurality of communication terminals subject for participation inthe session, as a session identification for identifying the session tobe established among the plurality of communication terminals.
 4. Thecontrol system of claim 3, wherein the processing circuitry of the firstcontrol apparatus generates the session identification for identifyingthe session to be established, so as to contain the relay deviceidentification information of the representative relay device.
 5. Acontrol apparatus, comprising: processing circuitry configured to obtaininformation regarding a plurality of relay devices for relaying contentdata in a session to be established among a plurality of communicationterminals, and determine one of the plurality of relay devices as arepresentative relay device to manage a relay destination of contentdata in the session to be established; a receiver configured to receive,from a first communication terminal of the plurality of communicationterminals subject for participation in the session, a request forstarting relay of content data; and a transmitter configured totransmit, with the request for starting relay of content data, relaydevice identification information for identifying the representativerelay device to a first relay device connected to the firstcommunication terminal, to cause the first relay device to furthertransmit the request for starting relay of content data to therepresentative relay device identified with the relay deviceidentification information of the representative relay device.
 6. Thecontrol apparatus of claim 5, wherein the receiver further receives,from a second communication terminal, an other request for startingrelay of content data including the relay device identificationinformation of the representative relay device, the second communicationterminal being a terminal other than the plurality of communicationterminals subject for participation in the session, and the transmitterfurther transmits the other request for starting relay of content datato a second relay device connected to the second communication terminal,to cause the second relay device to further transmit the other requestfor starting relay of content data to the representative relay deviceidentified with the relay device identification information of therepresentative relay device.
 7. The control apparatus of claim 5,wherein the transmitter further transmits the relay deviceidentification information of the representative relay device to theplurality of communication terminals subject for participation in thesession, before establishing the session in response to the request forstarting relay of content data.
 8. The control apparatus of claim 7,wherein the receiver receives the relay device identificationinformation of the representative relay device from the firstcommunication terminal, with the request for starting relay of contentdata, wherein the transmitter transmits, to the first relay device, therelay device identification information of the representative relaydevice that is received from the first communication terminal.
 9. Thecontrol apparatus of claim 8, wherein the processing circuitry generatessession identification information for identifying the session to beestablished among the plurality of communication terminals, andtransmits the session identification information to the plurality ofcommunication terminals subject for participation in the session, thesession identification information including the relay deviceidentification information of the representative relay device.
 10. Thecontrol apparatus of claim 9, further comprising: a memory configured tostore the session identification information including the relay deviceidentification information of the representative relay device, inassociation with identification information for identifying each one ofthe plurality of communication terminals participating in the session.11. A method of controlling a session, comprising: obtaining informationregarding a plurality of relay devices for relaying content data in asession to be established among a plurality of communication terminals,and determine one of the plurality of relay devices as a representativerelay device to manage a relay destination of content data in thesession to be established; receiving, from a first communicationterminal of the plurality of communication terminals subject forparticipation in the session, a request for starting relay of contentdata; and transmitting, with the request for starting relay of contentdata, relay device identification information for identifying therepresentative relay device to a first relay device connected to thefirst communication terminal, to cause the first relay device to furthertransmit the request for starting relay of content data to therepresentative relay device identified with the relay deviceidentification information of the representative relay device.
 12. Themethod of claim 11, further comprising: receiving, from a secondcommunication terminal, an other request for starting relay of contentdata including the relay device identification information of therepresentative relay device, the second communication terminal being aterminal other than the plurality of communication terminals subject forparticipation in the session; and transmitting the other request forstarting relay of content data to a second relay device connected to thesecond communication terminal, to cause the second relay device tofurther transmit the other request for starting relay of content data tothe representative relay device identified with the relay deviceidentification information of the representative relay device.
 13. Themethod of claim 11, further comprising: transmitting the relay deviceidentification information of the representative relay device to theplurality of communication terminals subject for participation in thesession, before establishing the session in response to the request forstarting relay of content data.
 14. The method of claim 13, furthercomprising: receiving the relay device identification information of therepresentative relay device from the first communication terminal, withthe request for starting relay of content data; and transmitting, to thefirst relay device, the relay device identification information of therepresentative relay device that is received from the firstcommunication terminal.
 15. The method of claim 14, further comprising:generating session identification information for identifying thesession to be established among the plurality of communicationterminals; and transmitting the session identification information tothe plurality of communication terminals subject for participation inthe session, the session identification information including the relaydevice identification information of the representative relay device.